Displaying 1-10 of 27 results found.
Coordination sequence for the Cairo or dual-3.3.4.3.4 tiling with respect to a trivalent point.
+0
25
1, 3, 8, 12, 15, 20, 25, 28, 31, 36, 41, 44, 47, 52, 57, 60, 63, 68, 73, 76, 79, 84, 89, 92, 95, 100, 105, 108, 111, 116, 121, 124, 127, 132, 137, 140, 143, 148, 153, 156, 159, 164, 169, 172, 175, 180, 185, 188, 191, 196, 201, 204, 207, 212, 217, 220, 223, 228
COMMENTS
There are two types of point in this tiling. This is the coordination sequence with respect to a point of degree 3.
The coordination sequence with respect to a point of degree 4 (see second illustration) is simply 1, 4, 8, 12, 16, 20, ..., the same as the coordination sequence for the 4.4.4.4 square grid ( A008574). See the CGS-NJAS link for the proof.
REFERENCES
Branko Grünbaum and G. C. Shephard, Tilings and Patterns. W. H. Freeman, New York, 1987. See Fig. 9.1.3, drawing P_5-24, page 480.
Herbert C. Moore, U.S. Patents 928,320 and 928,321, Patented July 20 1909. [Shows Cairo tiling.]
LINKS
Chung, Ping Ngai, Miguel A. Fernandez, Yifei Li, Michael Mara, Frank Morgan, Isamar Rosa Plata, Niralee Shah, Luis Sordo Vieira, and Elena Wikner. Isoperimetric Pentagonal Tilings, Notices of the AMS 59, no. 5 (2012), pp. 632-640. See Fig. 1 (left). N. J. A. Sloane, Coordination Sequences, Planing Numbers, and Other Recent Sequences (II), Experimental Mathematics Seminar, Rutgers University, Jan 31 2019, Part I, Part 2, Slides. (Mentions this sequence)
FORMULA
The simplest formula is: a(0)=1, a(1)=2, a(2)=8, and thereafter a(n) = 4n if n is odd, 4n - 1 if n == 0 (mod 4), and 4n+1 if n == 2 (mod 4). (See the CGS-NJAS link for proof. - N. J. A. Sloane, May 10 2018) G.f.: -(x^6-x^5-2*x^4-4*x^2-x-1)/((x^2+1)*(x-1)^2).
a(n) = (8*n - (-i)^n - i^n) / 2 for n>2, where i=sqrt(-1).
a(n) = 2*a(n-1) - 2*a(n-2) + 2*a(n-3) - a(n-4) for n>6.
(End)
MATHEMATICA
Join[{1, 3, 8}, LinearRecurrence[{2, -2, 2, -1}, {12, 15, 20, 25}, 100]] (* Jean-François Alcover, Aug 05 2018 *)
PROG
(PARI) See Links section.
CROSSREFS
List of coordination sequences for Laves tilings (or duals of uniform planar nets): [3,3,3,3,3.3] = A008486; [3.3.3.3.6] = A298014, A298015, A298016; [3.3.3.4.4] = A298022, A298024; [3.3.4.3.4] = A008574, A296368; [3.6.3.6] = A298026, A298028; [3.4.6.4] = A298029, A298031, A298033; [3.12.12] = A019557, A298035; [4.4.4.4] = A008574; [4.6.12] = A298036, A298038, A298040; [4.8.8] = A022144, A234275; [6.6.6] = A008458.
6, 30, 60, 180, 210, 2310, 4620, 60060, 510510, 10810800, 116396280, 200560490130, 401120980260
COMMENTS
The two sequences involve areas of primitive Pythagorean triples and primorial products. Intersections are only considered once (no repeats). Conjecture: the sequence is infinite.
Conjecture: The next two entries are a(12) = 200560490130, a(13) = 401120980260.
6|a(n) for n>=1,
30|a(n) for n>=2,
a(n)/6 = {1, 5, 10, 30, 35, 385, 770, 10010, ...} is a subset of values found in A008706. (End)
a(12) and a(13) confirmed. a(14) > 2*10^31, if it exists. - Giovanni Resta, Mar 31 2017
EXAMPLE
A024365 begins {6, 30, 60, 84, 180, 210, 210, 330, 504, 546, 630, 840, 924, 990, 1224, 1320, 1386, 1560, 1710, 1716, 2310, ...}.
A129912 begins {1, 2, 6, 12, 30, 60, 180, 210, 360, 420, 1260, 2310, 2520, ...}.
So, common entries encountered are {6, 30, 60, 180, 210, 2310, ...}.
These are then the first four entries of the sequence (6, 30, 60, 180).
MATHEMATICA
s = 6 Take[Sort[(Times @@ #)/12 & /@ ({Times @@ #, (Last[#]^2 - First[#]^2)/2} & /@ Select[Subsets[Range[1, 3600, 2], {2}], GCD @@ # == 1 &])], 1800]; f[m_] := f[m] = Union[Times @@@ Subsets[FoldList[Times, 1, Prime[Range[m]]]]][[1 ;; 100]]; f[10]; f[m = 11]; While[f[m] != f[m - 1], m++]; t = f[m]; Intersection[s, t] (* Michael De Vlieger, Oct 22 2015, after Harvey P. Dale at A020885 and Jean-François Alcover at A129912 *) (* or *) ok[n_] := Block[{a, f = Power @@@ FactorInteger[2 n]}, SelectFirst[ Subsets[f, {1, Floor[ Length[f]/2]}], (a = Times @@ #; IntegerQ@ Sqrt[a^2 + (2 n/a)^2]) &, {}] != {}]; pr[n_] := Product[ Prime[n+1-i]^i, {i, n}]; upto[mx_] := Block[{ric, j=1}, ric[n_, ip_, ex_] := If[n < mx, Block[{p = Prime[ip + 1]}, If[ex == 1 && ok[n], Sow@ n]; ric[n p^ex, ip + 1, ex]; If[ex > 1, ric[n p^(ex - 1), ip+1, ex-1]]]]; Sort@ Reap[ While[pr[j] < mx, ric[2^j, 1, j]; j++]][[2, 1]]]; upto[10^12] (* much faster, Giovanni Resta, Mar 31 2017 *)
PROG
(PARI)
\\note: code does not generate the sequence, just checks for a matching PPT entry
genit(area)={myMax=floor(sqrt(2*area)); i5=myMax; endless=0; soln=List();
while(i5>=2, dun=0; j=2.*myVal/i5; k=floor(j); if(j>k, dun=1 ); if(dun<1,
c=sqrt(i5^2 + k^2); w=floor(c); if(c>w, dun=1); if(dun<1, if(gcd(k, i5)>1, dun=1 ));
if(dun<1, listput(soln, k); listput(soln, i5); listput(soln, w); listsort(soln);
print("soln a, b, c = ", soln[1], " ", soln[2], " ", soln[3] ); dun=2; break ));
i5--; endless++); if(i5<=2&&dun<1, print("no solution ") ); if(i5>2&&dun<2,
print("max iteration limit was hit ", endless) ); print (endless); }
(C++)
#include <iostream>
#include <fstream>
using namespace std;
int main(){ifstream fin1, fin2;
int myValue, myValue2, ptr, fptr, i5, j5;
unsigned long list1[9999]={0};
unsigned long list2[999]={0};
unsigned long final[31]={0};
ptr=1;
while(ptr<9999)
{fin1>> myValue; fin1.get(); list1[ptr]=myValue;
if(ptr<999)
{fin2>> myValue2; fin2.get(); list2[ptr]=myValue2; }
ptr++; }
fin1.close(); fin2.close(); fptr=1;
for(i5=1; i5<9990; i5++)
{for(j5=1; j5<999; j5++){
if(list1[i5]==list2[j5] )
{
fptr++;
if(fptr>30){break; }
final[fptr]=list1[i5];
cout << final[fptr] << ", ";
break;
}}if(fptr>30){break; }}}
Coordination sequence of 2-uniform tiling {3.4.6.4, 4.6.12} with respect to a point of type 3.4.6.4.
+0
38
1, 4, 6, 7, 10, 14, 20, 24, 24, 23, 26, 34, 42, 44, 40, 37, 42, 54, 64, 64, 56, 51, 58, 74, 86, 84, 72, 65, 74, 94, 108, 104, 88, 79, 90, 114, 130, 124, 104, 93, 106, 134, 152, 144, 120, 107, 122, 154, 174, 164, 136, 121, 138, 174, 196, 184, 152, 135, 154, 194, 218
COMMENTS
Linear recurrence and g.f. confirmed by Shutov/Maleev link. - Ray Chandler, Aug 31 2023
REFERENCES
Branko Grünbaum and G. C. Shephard, Tilings and Patterns. W. H. Freeman, New York, 1987. See page 67, 4th row, 3rd tiling.
Otto Krötenheerdt, Die homogenen Mosaike n-ter Ordnung in der euklidischen Ebene, I, II, III, Wiss. Z. Martin-Luther-Univ. Halle-Wittenberg, Math-Natur. Reihe, 18 (1969), 273-290; 19 (1970), 19-38 and 97-122. [Includes classification of 2-uniform tilings]
Anton Shutov and Andrey Maleev, Coordination sequences of 2-uniform graphs, Z. Kristallogr., 235 (2020), 157-166.
FORMULA
Based on the b-file, the g.f. appears to be (-2*x^9+6*x^8-8*x^7+7*x^6-2*x^5-2*x^4+5*x^3-2*x^2+1) / (x^6-4*x^5+8*x^4-10*x^3+8*x^2-4*x+1). - N. J. A. Sloane, Dec 14 2015
MATHEMATICA
LinearRecurrence[{4, -8, 10, -8, 4, -1}, {1, 4, 6, 7, 10, 14, 20, 24, 24, 23}, 100] (* Paolo Xausa, Nov 15 2023 *)
CROSSREFS
See A265035 for the other type of point. Coordination sequences for the 20 2-uniform tilings in the order in which they appear in the Galebach catalog, together with their names in the RCSR database (two sequences per tiling): #1 krt A265035, A265036; #2 cph A301287, A301289; #3 krm A301291, A301293; #4 krl A301298, A298024; #5 krq A301299, A301301; #6 krs A301674, A301676; #7 krr A301670, A301672; #8 krk A301291, A301293; #9 krn A301678, A301680; #10 krg A301682, A301684; #11 bew A008574, A296910; #12 krh A301686, A301688; #13 krf A301690, A301692; #14 krd A301694, A219529; #15 krc A301708, A301710; #16 usm A301712, A301714; #17 krj A219529, A301697; #18 kre A301716, A301718; #19 krb A301720, A301722; #20 kra A301724, A301726.
Coordination sequence of 2-uniform tiling {3.4.6.4, 4.6.12} with respect to a point of type 4.6.12.
+0
37
1, 3, 6, 9, 11, 14, 17, 21, 25, 28, 30, 32, 35, 39, 43, 46, 48, 50, 53, 57, 61, 64, 66, 68, 71, 75, 79, 82, 84, 86, 89, 93, 97, 100, 102, 104, 107, 111, 115, 118, 120, 122, 125, 129, 133, 136, 138, 140, 143, 147, 151, 154, 156, 158, 161, 165, 169, 172, 174, 176
COMMENTS
Joseph Myers (Dec 14 2015) reports that "My program for coordination sequences requires describing the tiling structure under translation, listing all edges in the form: (class1, 0, 0) has an edge to (class2, x, y). The present tiling has 18 orbits of vertices under translation and 30 orbits of edges under translation (each of which is described in both directions). So in principle it could generate the other 19 2-uniform tilings, but without a cross check with hand-computed terms there's a risk of e.g. missing some edges, and a fair amount of work producing all the descriptions of translation classes of edges."
Linear recurrence and g.f. confirmed by Shutov/Maleev link. - Ray Chandler, Aug 31 2023
REFERENCES
Branko Grünbaum and G. C. Shephard, Tilings and Patterns. W. H. Freeman, New York, 1987. See page 67, 4th row, 3rd tiling.
Otto Krötenheerdt, Die homogenen Mosaike n-ter Ordnung in der euklidischen Ebene, I, II, III, Wiss. Z. Martin-Luther-Univ. Halle-Wittenberg, Math-Natur. Reihe, 18 (1969), 273-290; 19 (1970), 19-38 and 97-122. [Includes classification of 2-uniform tilings]
Anton Shutov and Andrey Maleev, Coordination sequences of 2-uniform graphs, Z. Kristallogr., 235 (2020), 157-166.
LINKS
N. J. A. Sloane, Coordination Sequences, Planing Numbers, and Other Recent Sequences (II), Experimental Mathematics Seminar, Rutgers University, Jan 31 2019, Part I, Part 2, Slides. (Mentions this sequence)
FORMULA
Based on the b-file, the g.f. appears to be (1+x^2+2*x^5-2*x^6+2*x^7-x^8)/(1-3*x+4*x^2-3*x^3+x^4). This matches the first 1000 terms, so is probably correct. - N. J. A. Sloane, Dec 14 2015 Conjectured g.f. is equivalent to a(n) = 3*n - A010892(n+1) for n >= 5. - R. J. Mathar, Oct 09 2020
MATHEMATICA
LinearRecurrence[{3, -4, 3, -1}, {1, 3, 6, 9, 11, 14, 17, 21, 25}, 100] (* Paolo Xausa, Nov 15 2023 *)
CROSSREFS
See A265036 for the other type of point. Coordination sequences for the 20 2-uniform tilings in the order in which they appear in the Galebach catalog, together with their names in the RCSR database (two sequences per tiling): #1 krt A265035, A265036; #2 cph A301287, A301289; #3 krm A301291, A301293; #4 krl A301298, A298024; #5 krq A301299, A301301; #6 krs A301674, A301676; #7 krr A301670, A301672; #8 krk A301291, A301293; #9 krn A301678, A301680; #10 krg A301682, A301684; #11 bew A008574, A296910; #12 krh A301686, A301688; #13 krf A301690, A301692; #14 krd A301694, A219529; #15 krc A301708, A301710; #16 usm A301712, A301714; #17 krj A219529, A301697; #18 kre A301716, A301718; #19 krb A301720, A301722; #20 kra A301724, A301726.
Coordination sequence of point of type 3.3.4.12 in 4-uniform tiling {3.3.4.3.4; 3.3.4.12; 3.3.12.4; 3.4.3.12}.
+0
4
1, 4, 9, 9, 12, 19, 21, 28, 27, 31, 38, 40, 48, 44, 49, 56, 57, 67, 63, 69, 73, 75, 85, 80, 88, 92, 95, 102, 98, 106, 109, 114, 121, 118, 123, 127, 132, 138, 137, 142, 147, 149, 156, 155, 159, 166, 168, 176, 172, 177, 184, 185, 195, 191, 197, 201, 203, 213, 208
COMMENTS
This tiling appears as an example in Connelly et al. (2014), Fig. 6 (the heavy black lines in the figures here are an artifact from that figure).
For the definition of k-uniform tiling see Section 2.2 of Chapter 2 of Grünbaum and Shephard (1987).
REFERENCES
Branko Grünbaum and G. C. Shephard, Tilings and Patterns. W. H. Freeman, New York, 1987.
LINKS
Brian Galebach, Tiling 132 (in list of 4-uniform tilings).
FORMULA
Empirical g.f.: -(2*x^16 +x^14 -2*x^12 -7*x^11 -10*x^10 -10*x^9 -14*x^8 -18*x^7 -17*x^6 -18*x^5 -12*x^4 -9*x^3 -9*x^2 -4*x -1) / ((x -1)^2*(x^4 +x^3 +x^2 +x +1)*(x^6 +x^5 +x^4 +x^3 +x^2 +x +1)). - Colin Barker, Dec 02 2014
Coordination sequence of point of type 3.4.3.12 in 4-uniform tiling {3.3.4.3.4; 3.3.4.12; 3.3.12.4; 3.4.3.12}.
+0
4
1, 4, 6, 11, 13, 15, 23, 23, 33, 30, 33, 42, 41, 54, 46, 54, 58, 58, 73, 64, 75, 74, 79, 89, 81, 94, 92, 100, 105, 102, 110, 109, 119, 123, 123, 126, 130, 135, 140, 142, 144, 151, 151, 161, 158, 161, 170, 169, 182, 174, 182, 186, 186, 201, 192, 203, 202, 207, 217
COMMENTS
This tiling appears as an example in Connelly et al. (2014), Fig. 6 (the heavy black lines in the figures here are an artifact from that figure).
For the definition of k-uniform tiling see Section 2.2 of Chapter 2 of Grünbaum and Shephard (1987).
REFERENCES
Branko Grünbaum and G. C. Shephard, Tilings and Patterns. W. H. Freeman, New York, 1987.
LINKS
Brian Galebach, Tiling 132 (in list of 4-uniform tilings).
FORMULA
Empirical g.f.: -(x^17 +x^16 +x^15 +x^14 -2*x^13 -4*x^12 -6*x^11 -7*x^10 -11*x^9 -18*x^8 -16*x^7 -19*x^6 -14*x^5 -13*x^4 -11*x^3 -6*x^2 -4*x -1) / ((x -1)^2*(x^4 +x^3 +x^2 +x +1)*(x^6 +x^5 +x^4 +x^3 +x^2 +x +1)). - Colin Barker, Dec 02 2014
Coordination sequence of point of type 3.3.12.4 in 4-uniform tiling {3.3.4.3.4; 3.3.4.12; 3.3.12.4; 3.4.3.12}.
+0
4
1, 4, 7, 10, 15, 16, 21, 29, 28, 34, 33, 40, 48, 45, 53, 51, 59, 65, 64, 72, 68, 78, 83, 83, 89, 87, 97, 100, 102, 107, 106, 114, 119, 121, 124, 125, 132, 138, 138, 143, 144, 149, 157, 156, 162, 161, 168, 176, 173, 181, 179, 187, 193, 192, 200, 196, 206, 211, 211
COMMENTS
This tiling appears as an example in Connelly et al. (2014), Fig. 6 (the heavy black lines in the figures here are an artifact from that figure).
For the definition of k-uniform tiling see Section 2.2 of Chapter 2 of Grünbaum and Shephard (1987).
REFERENCES
Branko Grünbaum and G. C. Shephard, Tilings and Patterns. W. H. Freeman, New York, 1987.
LINKS
Brian Galebach, Tiling 132 (in list of 4-uniform tilings).
FORMULA
Empirical g.f.: -(3*x^14 -4*x^12 -4*x^11 -7*x^10 -12*x^9 -14*x^8 -21*x^7 -17*x^6 -15*x^5 -15*x^4 -10*x^3 -7*x^2 -4*x -1) / ((x -1)^2*(x^4 +x^3 +x^2 +x +1)*(x^6 +x^5 +x^4 +x^3 +x^2 +x +1)). - Colin Barker, Dec 02 2014
Coordination sequence of point of type 3.3.4.3.4 in 4-uniform tiling {3.3.4.3.4; 3.3.4.12; 3.3.12.4; 3.4.3.12}.
+0
4
1, 5, 8, 8, 11, 17, 25, 27, 24, 30, 38, 46, 47, 44, 46, 50, 64, 68, 65, 66, 70, 80, 80, 83, 87, 91, 100, 100, 99, 99, 109, 121, 121, 119, 119, 125, 133, 139, 140, 140, 145, 153, 155, 152, 158, 166, 174, 175, 172, 174, 178, 192, 196, 193, 194, 198, 208, 208, 211
COMMENTS
This tiling appears as an example in Connelly et al. (2014), Fig. 6 (the heavy black lines in the figures here are an artifact from that figure).
For the definition of k-uniform tiling see Section 2.2 of Chapter 2 of Grünbaum and Shephard (1987).
REFERENCES
Branko Grünbaum and G. C. Shephard, Tilings and Patterns. W. H. Freeman, New York, 1987.
LINKS
Brian Galebach, Tiling 132 (in list of 4-uniform tilings).
FORMULA
Empirical g.f.: -(x+1)*(x^15 +3*x^14 -4*x^11 -6*x^10 -7*x^9 -4*x^8 -7*x^7 -11*x^6 -9*x^5 -7*x^4 -4*x^3 -4*x^2 -4*x -1) / ((x -1)^2*(x^4 +x^3 +x^2 +x +1)*(x^6 +x^5 +x^4 +x^3 +x^2 +x +1)). - Colin Barker, Dec 02 2014
Coordination sequence for planar net 3.12.12.
+0
34
1, 3, 4, 6, 8, 12, 14, 15, 18, 21, 22, 24, 28, 30, 30, 33, 38, 39, 38, 42, 48, 48, 46, 51, 58, 57, 54, 60, 68, 66, 62, 69, 78, 75, 70, 78, 88, 84, 78, 87, 98, 93, 86, 96, 108, 102, 94, 105, 118, 111, 102, 114, 128, 120, 110, 123, 138, 129
COMMENTS
Also, growth series for group with presentation < S, T : S^2 = T^3 = (S*T)^6 = 1 >. See Magma program in A298805. - N. J. A. Sloane, Feb 06 2018
LINKS
Reticular Chemistry Structure Resource, hca
FORMULA
Empirically,
a(4n) = 10n - 2 except for a(0) = 1
a(4n+1) = 9n + 3
a(4n+2) = 8n + 6 except for a(2) = 4
a(4n+3) = 9n + 6. (End)
If these are correct, the sequence has g.f.
-(-1 - x - x^2 - 3*x^3 + x^4 - 5*x^5 + 3*x^6 - 4*x^7 + 2*x^8)/((x - 1)^2*(x^2 + 1)^2). - N. J. A. Sloane, Nov 28 2014 E.g.f.: (9*x*cosh(x) - 4*(2*cos(x) + x^2 - 3) + 9*x*sinh(x) - (x - 3)*sin(x))/4. - Stefano Spezia, Jan 05 2023
MATHEMATICA
Join[{1, 3, 4}, LinearRecurrence[{2, -3, 4, -3, 2, -1}, {6, 8, 12, 14, 15, 18}, 100]] (* Jean-François Alcover, Aug 05 2018 *)
EXTENSIONS
a(8) onwards from Maurizio Paolini and Joseph Myers (independently), Nov 28 2014
Coordination sequence for planar net 3.3.3.3.6 (also called the fsz net).
+0
6134
1, 5, 9, 15, 19, 24, 29, 33, 39, 43, 48, 53, 57, 63, 67, 72, 77, 81, 87, 91, 96, 101, 105, 111, 115, 120, 125, 129, 135, 139, 144, 149, 153, 159, 163, 168, 173, 177, 183, 187, 192, 197, 201, 207, 211, 216, 221, 225, 231, 235
COMMENTS
There are eleven uniform (or Archimedean) tilings (or planar nets), with vertex symbols 3^6, 3^4.6, 3^3.4^2, 3^2.4.3.4, 4^4, 3.4.6.4, 3.6.3.6, 6^3, 3.12^2, 4.6.12, and 4.8^2. Grünbaum and Shephard (1987) is the best reference.
a(n) is the number of vertices at graph distance n from any fixed vertex.
The Mathematica notebook can compute 30 or 40 iterations, and colors them with period 5. You could also change out images if you want to. These graphs are better for analyzing 5-iteration chunks of the pattern. You can see that under iteration all fragments of the circumferences are preserved in shape and translated outwards a distance approximately sqrt(21) (relative to small triangle edge), the length of a long diagonal of larger rhombus unit cell. The conjectured recurrence should follow from an analysis of how new pieces occur in between the translated pieces. - Bradley Klee, Nov 26 2014
REFERENCES
Branko Grünbaum and G. C. Shephard, Tilings and Patterns. W. H. Freeman, New York, 1987, Fig. 2.1.5, p. 63.
Marjorie Senechal, Quasicrystals and geometry, Cambridge University Press, Cambridge, 1995, Fig. 1.10, Section 1.3, pp. 13-16.
LINKS
Reticular Chemistry Structure Resource, fszN. J. A. Sloane, Coordination Sequences, Planing Numbers, and Other Recent Sequences (II), Experimental Mathematics Seminar, Rutgers University, Jan 31 2019, Part 1, Part 2, Slides. (Mentions this sequence)
FORMULA
Based on the computations of Darrah Chavey, Bradley Klee, and Maurizio Paolini, there is a strong conjecture that the first differences of this sequence are 4, 4, 6, 4, 5, 5, 4, 6, 4, 5, 5, 4, 6, 4, 5, 5, ..., that is, 4 followed by (4,6,4,5,5) repeated.
This would imply that the sequence satisfies the recurrence:
for n > 2, a(n) = a(n-1) + { n == 0,3 (mod 5), 4; n == 4 (mod 5), 6; n == 1,2 (mod 5), 5 }
(from Darrah Chavey)
and has generating function
(x^2+x+1)*(x^4+3*x^3+3*x+1)/((x^4+x^3+x^2+x+1)*(x-1)^2)
All the above conjectures are true - for proof see link to my article with Chaim Goodman-Strauss. - N. J. A. Sloane, Jan 14 2018; link added Mar 26 2018
MATHEMATICA
CoefficientList[Series[(x^2+x+1)(x^4+3x^3+3x+1)/((x^4+x^3+x^2+x+1)(x-1)^2), {x, 0, 80}], x] (* or *) LinearRecurrence[{1, 0, 0, 0, 1, -1}, {1, 5, 9, 15, 19, 24, 29}, 60] (* Harvey P. Dale, May 05 2018 *)
PROG
(C) /* Comments on the C program (see link) from Maurizio Paolini, Nov 23 2014: Basically what I do is deform the net onto the integral lattice, connect nodes aligned either horizontally, vertically or diagonally from northeast to southwest, marking as UNREACHABLE the nodes with coordinates (i, j) satisfying i + 2*j = 0 mod 7. Then the code computes the distance from each node to the central node of the grid. */
CROSSREFS
For partial sums of the present sequence, see A250121.
EXTENSIONS
a(11)-a(49) from Maurizio Paolini, Nov 23 2014
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