Displaying 1-10 of 15 results found.
Number of incongruent ways to tile a 3 X 2n room with 1x2 Tatami mats. At most 3 Tatami mats may meet at a point.
+10
7
2, 2, 2, 4, 5, 9, 12, 21, 30, 51, 76, 127, 195, 322, 504, 826, 1309, 2135, 3410, 5545, 8900, 14445, 23256, 37701, 60813, 98514, 159094, 257608, 416325, 673933, 1089648, 1763581, 2852242, 4615823, 7466468, 12082291, 19546175, 31628466
FORMULA
For n >= 8, a(n) = a(n-1) + 2*a(n-2) - a(n-3) - a(n-5) - a(n-6).
a(n) = (-1)^(n-1)*(a(n-1) - a(n-2)), a(1)=1, a(2)=1.
+10
6
1, 1, 0, 1, 1, 0, -1, 1, 2, -1, -3, 2, 5, -3, -8, 5, 13, -8, -21, 13, 34, -21, -55, 34, 89, -55, -144, 89, 233, -144, -377, 233, 610, -377, -987, 610, 1597, -987, -2584, 1597, 4181, -2584, -6765, 4181, 10946, -6765, -17711, 10946, 28657, -17711, -46368
FORMULA
G.f.: x*(1 + x + x^2 + 2*x^3)/(1 + x^2 - x^4).
a(n) = -a(n-2) + a(n-4). (End)
a(n) = b(n-1) + b(n-2) + b(n-3) + 2*b(n-4), where b(n) = i^n * A079977(n). - G. C. Greubel, Dec 06 2022
MATHEMATICA
LinearRecurrence[{0, -1, 0, 1}, {1, 1, 0, 1}, 60] (* Harvey P. Dale, May 08 2017 *)
PROG
(PARI) a(n)=fibonacci((3-n)\2+(3-n)%2*2)
(Sage)
x, y, b = 1, 1, true
while True:
yield x
x, y = y, x - y
y = -y if b else y
b = not b
(Magma) [Fibonacci(1 -Floor((n-4)/2) -2*((n-4) mod 2)): n in [1..60]]; // G. C. Greubel, Dec 06 2022
AUTHOR
Klaus Strassburger (strass(AT)ddfi.uni-duesseldorf.de), Dec 10 1999
1, 2, 1, 3, 2, 5, 3, 8, 5, 13, 8, 21, 13, 34, 21, 55, 34, 89, 55, 144, 89, 233, 144, 377, 233, 610, 377, 987, 610, 1597, 987, 2584, 1597, 4181, 2584, 6765, 4181, 10946, 6765, 17711, 10946, 28657, 17711, 46368, 28657, 75025, 46368, 121393, 75025, 196418
COMMENTS
All terms are Fibonacci numbers A000045: a(2n-1) = Fibonacci(n), a(2n) = Fibonacci(n+2), a(2n-1) = a(2n+2). - Alexander Adamchuk, Oct 08 2006
FORMULA
a(n) = Fibonacci(3/4 -(-1)^(n+1)*3/4 +(n+1)/2). (End)
G.f. -x*(1+2*x+x^3) / ( -1+x^2+x^4 ). - R. J. Mathar, Mar 08 2011
MAPLE
seq(coeff(series(-x*(1+2*x+x^3)/(x^4+x^2-1), x, n+1), x, n), n = 1 .. 50); # Muniru A Asiru, Oct 12 2018
MATHEMATICA
p[0, x] = 1; p[1, x] = x + 1; p[k_, x_] := p[k, x] = x*p[k - 1, x] + (-1)^(n + 1)p[k - 2, x]; Table[Sum[CoefficientList[p[n, x], x][[m]], {m, 1, n + 1}], {n, 0, 20}]
Rest[Flatten[Reverse/@Partition[Fibonacci[Range[30]], 2, 1]]] (* Harvey P. Dale, Mar 19 2013 *)
PROG
(PARI) vector(50, n, fibonacci(3/4 -(-1)^(n+1)*3/4 +(n+1)/2)) \\ G. C. Greubel, Oct 12 2018
(Magma) m:=50; R<x>:=PowerSeriesRing(Integers(), m); Coefficients(R!(x*(1 + 2*x + x^3)/(1 - x^2 - x^4))); // G. C. Greubel, Oct 12 2018
(GAP) a:=[1, 2, 1, 3];; for n in [5..50] do a[n]:=a[n-2]+a[n-4]; od; a; # Muniru A Asiru, Oct 12 2018
Triangle read by rows: T(n,k) = number of palindromic compositions of n in which the largest part is equal to k, 1 <= k <= n.
+10
4
1, 1, 1, 1, 0, 1, 1, 2, 0, 1, 1, 1, 1, 0, 1, 1, 4, 1, 1, 0, 1, 1, 2, 3, 0, 1, 0, 1, 1, 7, 3, 3, 0, 1, 0, 1, 1, 4, 6, 1, 2, 0, 1, 0, 1, 1, 12, 7, 7, 1, 2, 0, 1, 0, 1, 1, 7, 12, 3, 5, 0, 2, 0, 1, 0, 1, 1, 20, 16, 15, 3, 5, 0, 2, 0, 1, 0, 1
COMMENTS
A palindromic composition of a natural number m is an ordered partition of m into N+1 natural numbers (or parts), p_0, p_1, ..., p_N, of the form m = p_0 + p_1 + ... + p_N such that p_j = p_{N-j}, for each j in {0,...,N}. Two palindromic compositions, sum_{j=0..N} p_j and sum_{j=0..N} q_j (say), are identical if and only if p_j = q_j, j = 0,...,N; otherwise they are taken to be distinct.
EXAMPLE
There are eight palindromic compositions of n=7, namely, {7}, {3,1,3}, {2,3,2}, {2,1,1,1,2}, {1,5,1}, {1,2,1,2,1}, {1,1,3,1,1}, {1,1,1,1,1,1,1}, and three of them have the largest part equal to 3, so T(7,3) = 3.
Triangle T(n,k) begins:
1;
1, 1;
1, 0, 1,
1, 2, 0, 1;
1, 1, 1, 0, 1;
1, 4, 1, 1, 0, 1;
1, 2, 3, 0, 1, 0, 1;
1, 7, 3, 3, 0, 1, 0, 1;
1, 4, 6, 1, 2, 0, 1, 0, 1;
1, 12, 7, 7, 1, 2, 0, 1, 0, 1;
...
MAPLE
b:= proc(n, k) option remember; `if`(n<=k, 1, 0)+
add(b(n-2*j, k), j=1..min(k, iquo(n, 2)))
end:
T:= (n, k)-> b(n, k) -b(n, k-1):
MATHEMATICA
b[n_, k_] := b[n, k] = If[n <= k, 1, 0] + Sum[b[n-2*j, k], { j, 1, Min[k, Quotient[n, 2]]}]; t[n_, k_] := b[n, k] - b[n, k-1]; Table[Table[t[n, k], {k, 1, n}], {n, 1, 14}] // Flatten (* Jean-François Alcover, Dec 13 2013, translated from Alois P. Heinz's Maple code *)
PROG
(PARI) T(n, k, ok=0)={
if(n<1, return(n==0 && ok));
if(k>n/2 && !ok,
n-=k;
if(n<0||n%2, return(0));
return(2^max(n/2-1, 0))
);
sum(i=1, k,
T(n-2*i, k, ok||i==k)
)+(n==k || (ok && n<k))
Triangle read by rows: T(n,k) = number of palindromic compositions of n in which no part exceeds k, 1 <= k <= n.
+10
4
1, 1, 2, 1, 1, 2, 1, 3, 3, 4, 1, 2, 3, 3, 4, 1, 5, 6, 7, 7, 8, 1, 3, 6, 6, 7, 7, 8, 1, 8, 11, 14, 14, 15, 15, 16, 1, 5, 11, 12, 14, 14, 15, 15, 16, 1, 13, 20, 27, 28, 30, 30, 31, 31, 32, 1, 8, 20, 23, 28, 28, 30, 30, 31, 31, 32, 1, 21, 37, 52, 55, 60, 60, 62, 62, 63, 63, 64
COMMENTS
A palindromic composition of a natural number m is an ordered partition of m into N+1 natural numbers (or parts), p_0, p_1, ..., p_N, of the form m = p_0 + p_1 + ... + p_N such that p_j = p_{N-j}, for each j in {0,...,N}. Two palindromic compositions, sum_{j=0..N} p_j and sum_{j=0..N} q_j (say), are identical if and only if p_j = q_j, j = 0,...,N; otherwise they are taken to be distinct.
EXAMPLE
Triangle T(n,k) begins:
1;
1, 2;
1, 1, 2;
1, 3, 3, 4;
1, 2, 3, 3, 4;
1, 5, 6, 7, 7, 8;
1, 3, 6, 6, 7, 7, 8;
1, 8, 11, 14, 14, 15, 15, 16;
1, 5, 11, 12, 14, 14, 15, 15, 16;
1, 13, 20, 27, 28, 30, 30, 31, 31, 32;
MAPLE
T:= proc(n, k) option remember; `if`(n<=k, 1, 0)+
add(T(n-2*j, k), j=1..min(k, iquo(n, 2)))
end:
MATHEMATICA
T[n_, k_] := T[n, k] = If[n <= k, 1, 0] + Sum[T[n-2*j, k], {j, 1, Min[k, Quotient[ n, 2]]}]; Table[Table[T[n, k], {k, 1, n}], {n, 1, 14}] // Flatten (* Jean-François Alcover, Mar 09 2015, after Alois P. Heinz *)
"BHK" (reversible, identity, unlabeled) transform of 1,0,1,0...(odds).
+10
2
1, 0, 1, 1, 2, 3, 5, 9, 14, 25, 39, 68, 107, 182, 289, 483, 772, 1275, 2047, 3355, 5402, 8811, 14213, 23112, 37325, 60580, 97905, 158717, 256622, 415715, 672337, 1088661, 1760998, 2850645, 4611643, 7463884, 12075527, 19541994
FORMULA
G.f.: x*(1-x-2*x^2+2*x^3+x^6)/((1-x)*(1+x)*(1-x-x^2)*(1-x^2-x^4)).
a(n) = a(n-1) + 3*a(n-2) - 2*a(n-3) - 2*a(n-4) - a(n-6) + a(n-7) + a(n-8) for n > 8. - Andrew Howroyd, Aug 31 2018
PROG
(PARI) Vec((1-x-2*x^2+2*x^3+x^6)/((1-x)*(1+x)*(1-x-x^2)*(1-x^2-x^4)) + O(x^40)) \\ Andrew Howroyd, Aug 31 2018
a(n) = (a(n-1) mod a(n-2)) + a(n-2), a(0) = 3, a(1) = 2.
+10
2
2, 5, 3, 8, 5, 13, 8, 21, 13, 34, 21, 55, 34, 89, 55, 144, 89, 233, 144, 377, 233, 610, 377, 987, 610, 1597, 987, 2584, 1597, 4181, 2584, 6765, 4181, 10946, 6765, 17711, 10946, 28657, 17711, 46368, 28657, 75025, 46368, 121393, 75025, 196418, 121393, 317811, 196418, 514229, 317811, 832040, 514229
FORMULA
a(2n) = Fibonacci(n+4), a(2n+1) = Fibonacci(n+3).
G.f.: (2 + 5*x + x^2 + 3*x^3)/(1 - x^2 - x^4). - G. C. Greubel, Dec 06 2022
MATHEMATICA
LinearRecurrence[{0, 1, 0, 1}, {2, 5, 3, 8}, 60] (* G. C. Greubel, Dec 06 2022 *)
PROG
(Magma) [Fibonacci(3 +Floor(n/2) +2*(n mod 2)): n in [0..60]]; // G. C. Greubel, Dec 06 2022
(SageMath) [fibonacci(3 +(n//2) + 2*(n%2)) for n in range(61)] # G. C. Greubel, Dec 06 2022
Difference sequence of the sequence A116470 of all distinct Fibonacci numbers and Lucas numbers ( A000032).
+10
2
1, 1, 1, 1, 2, 1, 3, 2, 5, 3, 8, 5, 13, 8, 21, 13, 34, 21, 55, 34, 89, 55, 144, 89, 233, 144, 377, 233, 610, 377, 987, 610, 1597, 987, 2584, 1597, 4181, 2584, 6765, 4181, 10946, 6765, 17711, 10946, 28657, 17711, 46368, 28657, 75025, 46368, 121393, 75025
COMMENTS
Every term is a Fibonacci number ( A000045).
FORMULA
a(n) = a(n-2)+a(n-4) for n>4.
G.f.: x*(1+x-x^5) / (1-x^2-x^4).
(End)
EXAMPLE
A116470 = (1, 2, 3, 4, 5, 7, 8, 11, 13, 18, 21, 29, 34, 47, 55, 76,...), so that (a(n)) = (1,1,1,1,2,1,3,2,5,3,8,5,13,8,12,...).
MATHEMATICA
u = Table[Fibonacci[n], {n, 1, 200}]; v = Table[LucasL[n], {n, 1, 200}];
Take[Differences[Union[u, v]], 100]
PROG
(PARI) Vec(x*(1+x-x^5)/(1-x^2-x^4) + O(x^50)) \\ Colin Barker, May 10 2016
Triangular array read by rows: T(n,k) is the number of palindromic compositions of n having exactly k 1's, n>=0, 0<=k<=n.
+10
1
1, 0, 1, 1, 0, 1, 1, 0, 0, 1, 2, 0, 1, 0, 1, 1, 1, 1, 0, 0, 1, 3, 0, 3, 0, 1, 0, 1, 2, 1, 1, 2, 1, 0, 0, 1, 5, 0, 5, 0, 4, 0, 1, 0, 1, 3, 2, 3, 2, 1, 3, 1, 0, 0, 1, 8, 0, 10, 0, 7, 0, 5, 0, 1, 0, 1, 5, 3, 5, 5, 4, 3, 1, 4, 1, 0, 0, 1, 13, 0, 18, 0, 16, 0, 9, 0, 6, 0, 1, 0, 1, 8, 5, 10, 8, 7, 9, 5, 4, 1, 5, 1, 0, 0, 1
FORMULA
G.f.: G(x,y) = ((1 + x)*(1 - x + x^2 + x*y - x^2*y))/(1 - x^2 - x^4 - x^2*y^2 + x^4*y^2). Satisfies G(x,y) = 1/(1 - x) - x + y*x + (x^2/(1 - x^2) - x^2 +y^2*x^2)*G(x,y).
EXAMPLE
1,
0, 1,
1, 0, 1,
1, 0, 0, 1,
2, 0, 1, 0, 1,
1, 1, 1, 0, 0, 1,
3, 0, 3, 0, 1, 0, 1,
2, 1, 1, 2, 1, 0, 0, 1,
5, 0, 5, 0, 4, 0, 1, 0, 1,
3, 2, 3, 2, 1, 3, 1, 0, 0, 1
There are eight palindromic compositions of 6: T(6,0)=3 because we have: 6, 3+3, 2+2+2. T(6,2)=3 because we have: 1+4+1, 2+1+1+2, 1+2+2+1. T(6,4)=1 because we have: 1+1+2+1+1. T(6,6)=1 because we have: 1+1+1+1+1+1.
MAPLE
b:= proc(n) option remember; `if`(n=0, 1, expand(
add(b(n-j)*`if`(j=1, x^2, 1), j=1..n)))
end:
T:= n-> (p-> seq(coeff(p, x, i), i=0..n))
(add(b(i)*`if`(n-2*i=1, x, 1), i=0..n/2)):
MATHEMATICA
nn=15; Table[Take[CoefficientList[Series[((1+x)*(1-x+x^2+x*y-x^2*y))/(1-x^2-x^4-x^2*y^2+x^4*y^2), {x, 0, nn}], {x, y}][[n]], n], {n, 1, nn}]//Grid
Triangle read by rows: T(n,k) is the number of 00-avoiding binary words of length n having degree of asymmetry equal to k (n>=0; 0<=k<=floor(n/2)).
+10
1
1, 2, 1, 2, 3, 2, 2, 4, 2, 5, 6, 2, 3, 8, 8, 2, 8, 14, 10, 2, 5, 16, 20, 12, 2, 13, 30, 30, 14, 2, 8, 30, 48, 40, 16, 2, 21, 60, 78, 54, 18, 2, 13, 56, 106, 112, 68, 20, 2, 34, 116, 184, 166, 86, 22, 2, 21, 102, 224, 286, 224, 104, 24, 2, 55, 218, 408, 452, 310, 126, 26, 2
COMMENTS
The degree of asymmetry of a finite sequence of numbers is defined to be the number of pairs of symmetrically positioned distinct entries. Example: the degree of asymmetry of (2,7,6,4,5,7,3) is 2, counting the pairs (2,3) and (6,5).
A sequence is palindromic if and only if its degree of asymmetry is 0.
Number of entries in row n is 1+floor(n/2).
Sum of entries in row n is A000045(n+2) (Fibonacci).
T(n,0) = A053602(n+2) (= number of palindromic 00-avoiding binary words of length n).
FORMULA
G.f.: G(t,z) = (1 + 2z + tz^2 +z^3 -tz^5)/(1 - z^2 - tz^2 - z^4 - tz^4 + tz^6).
EXAMPLE
Row 3 is [3,2] because the 00-avoiding binary words of length 3 are 010, 011, 101, 110, 111, having asymmetry degrees 0, 1, 0, 1, 0, respectively.
Triangle starts:
1;
2;
1,2;
3,2;
2,4,2;
5,6,2.
MAPLE
G := (1+2*z+t*z^2+z^3-t*z^5)/(1-z^2-t*z^2-z^4-t*z^4+t*z^6): Gser := simplify(series(G, z = 0, 20)): for n from 0 to 18 do P[n] := sort(coeff(Gser, z, n)) end do: for n from 0 to 18 do seq(coeff(P[n], t, j), j = 0 .. (1/2)*n) end do; # yields sequence in triangular form
MATHEMATICA
Table[BinCounts[#, {0, Floor[n/2] + 1, 1}] &@ Map[Total@ BitXor[Take[#, Ceiling[Length[#]/2]], Reverse@ Take[#, -Ceiling[Length[#]/2]]] &, Select[PadLeft[IntegerDigits[#, 2], n] & /@ Range[0, 2^n - 1], Length@ SequenceCases[#, {0, 0}] == 0 &]], {n, 0, 15}] // Flatten (* Michael De Vlieger, Aug 15 2016, Version 10.1 *)
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