A017377 -id:A017377

A161365

a(n) = 3/2 + 5*n - 5*(-1)^n/2.

+0
1

9, 9, 19, 19, 29, 29, 39, 39, 49, 49, 59, 59, 69, 69, 79, 79, 89, 89, 99, 99, 109, 109, 119, 119, 129, 129, 139, 139, 149, 149, 159, 159, 169, 169, 179, 179, 189, 189, 199, 199, 209, 209, 219, 219, 229, 229, 239, 239, 249, 249, 259, 259, 269, 269, 279, 279, 289

(list; graph; refs; listen; history; text; internal format)

OFFSET

1,1

LINKS

Vincenzo Librandi, Table of n, a(n) for n = 1..1000

Index entries for linear recurrences with constant coefficients, signature (1,1,-1).

FORMULA

a(n) = 10*n - a(n-1) - 2, n > 1.

a(n+1) = A017377(floor(n/2)). - R. J. Mathar, Jan 05 2011

G.f.: x*(9+x^2) / ( (1+x)*(x-1)^2 ). - R. J. Mathar, Jan 05 2011

MATHEMATICA

LinearRecurrence[{1, 1, -1}, {9, 9, 19}, 60] (* Vincenzo Librandi, Mar 02 2012 *)

Table[3/2+5n-(5(-1)^n)/2, {n, 60}] (* or *) nxt[{n_, a_}]:={n+1, 10(n+1)-a-2}; NestList[nxt, {1, 9}, 60][[;; , 2]] (* Harvey P. Dale, Nov 04 2024 *)

PROG

(Magma) I:=[9, 9, 19]; [n le 3 select I[n] else Self(n-1)+Self(n-2)-Self(n-3): n in [1..60]]; // Vincenzo Librandi, Mar 02 2012

(PARI) for(n=1, 60, print1(3/2+5*n-5*(-1)^n/2", ")); \\ Vincenzo Librandi, Mar 02 2012

KEYWORD

nonn,easy

AUTHOR

Vincenzo Librandi, Nov 25 2009

EXTENSIONS

Definition rewritten by R. J. Mathar, Jan 05 2011

STATUS

approved

A346953

a(n) is the number of divisors of A346950(n) ending with 3.

+0
3

1, 2, 2, 2, 2, 2, 1, 2, 2, 2, 2, 2, 2, 2, 2, 2, 4, 2, 2, 2, 1, 2, 2, 2, 2, 2, 2, 2, 2, 2, 4, 2, 4, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 3, 2, 2, 2, 4, 2, 2, 2, 2, 2, 2, 2, 2, 4, 4, 2, 2, 2, 2, 2, 4, 2, 2, 2, 2, 2, 2, 4, 2, 2, 2, 1, 2, 2, 2, 2, 2, 2, 4, 2, 2, 4, 2, 2

(list; graph; refs; listen; history; text; internal format)

OFFSET

1,2

COMMENTS

a(n) = 1 if A346950(n) = k^2 where k is either a prime ending with 3 or the product of a prime ending with 7 and a prime ending with 9. - Robert Israel, Nov 03 2024

LINKS

Robert Israel, Table of n, a(n) for n = 1..10000

EXAMPLE

a(17) = 4 since there are 4 divisors of A346950(17) = 429 ending with 3: 3, 13, 33 and 143.

MAPLE

N:= 10000: # for a(1) .. a(M) where the last term of A346950 less than N is A346950(M)

S:= {}:

for n from 3 to floor(sqrt(N)) by 10 do

S:= S union map(`*`, {seq(i, i= n .. floor(N/n), 10)}, n)

od:

S:= sort(convert(S, list)):

map(t -> nops(select(t -> t mod 10 = 3, numtheory:-divisors(t))), S); # Robert Israel, Nov 03 2024

MATHEMATICA

b={}; For[n=0, n<=450, n++, For[k=0, k<=n, k++, If[Mod[10*n+9, 10*k+3]==0 && Mod[(10*n+9)/(10*k+3), 10]==3 && 10*n+9>Max[b], AppendTo[b, 10*n+9]]]]; (* A346950 *) a={}; For[i =1, i<=Length[b], i++, AppendTo[a, Length[Drop[Select[Divisors[Part[b, i]], (Mod[#, 10]==3&)]]]]]; a

PROG

(Python)

from sympy import divisors

def f(n): return sum(d%10 == 3 for d in divisors(n)[1:-1])

def A346950upto(lim): return sorted(set(a*b for a in range(3, lim//3+1, 10) for b in range(a, lim//a+1, 10)))

print(list(map(f, A346950upto(2129)))) # Michael S. Branicky, Aug 11 2021

CROSSREFS

Cf. A000005, A017377, A346388 (ending with 5), A346389 (ending with 6), A346950, A346951, A346952.

KEYWORD

nonn,base

AUTHOR

Stefano Spezia, Aug 08 2021

STATUS

approved

A266297

Numbers whose last digit is a square.

+0
1

0, 1, 4, 9, 10, 11, 14, 19, 20, 21, 24, 29, 30, 31, 34, 39, 40, 41, 44, 49, 50, 51, 54, 59, 60, 61, 64, 69, 70, 71, 74, 79, 80, 81, 84, 89, 90, 91, 94, 99, 100, 101, 104, 109, 110, 111, 114, 119, 120, 121, 124, 129, 130, 131, 134, 139, 140, 141, 144, 149

(list; graph; refs; listen; history; text; internal format)

OFFSET

1,3

COMMENTS

Numbers ending in 0, 1, 4 and 9.

Union of A008592, A017281, A017317 and A017377. - Hurt

None of these numbers are prime in Z[phi] (where phi = 1/2 + sqrt(5)/2 is the golden ratio), since the numbers in this sequence that are prime in Z can be expressed in the form (a - b sqrt(5))(a + b sqrt(5)). - Alonso del Arte, Dec 30 2015

Union of A197652 and A016897. - Wesley Ivan Hurt, Dec 31 2015

Union of A146763 and A090771. - Wesley Ivan Hurt, Jan 01 2016

LINKS

G. C. Greubel, Table of n, a(n) for n = 1..5000

Index entries for linear recurrences with constant coefficients, signature (1,0,0,1,-1).

FORMULA

G.f.: x^2*(1 + 3*x + 5*x^2 + x^3)/((x - 1)^2*(1 + x + x^2 + x^3)).

a(n) = a(n - 1) + (n - 4) - a(n - 5) for n > 5.

a(n) = (10n - 11 + (-1)^n + (4 + 2(-1)^n) * (-1)^((2n - 1 + (-1)^n)/4))/4.

a(n+1) - a(n) = A091084(n+1) for n>0.

Sum_{n>=2} (-1)^n/a(n) = (14*sqrt(5)*arccoth(sqrt(5)) - 2*Pi*sqrt(1-2/sqrt(5)) + 16*log(2) + 5*log(5))/40. - Amiram Eldar, Jul 30 2024

MAPLE

A266297:=n->(10*n-11+(-1)^n+(4+2*(-1)^n)*(-1)^((2*n-1+(-1)^n)/4))/4: seq(A266297(n), n=1..100);

MATHEMATICA

Table[(10 n - 11 + (-1)^n + (4 + 2 (-1)^n)*(-1)^((2 n - 1 + (-1)^n)/4))/4, {n, 50}] (* G. C. Greubel, Dec 27 2015 *)

LinearRecurrence[{1, 0, 0, 1, -1}, {0, 1, 4, 9, 10}, 60] (* Vincenzo Librandi, Dec 27 2015 *)

CoefficientList[Series[x*(1 + 3*x + 5*x^2 + x^3)/((x - 1)^2*(1 + x + x^2 + x^3)), {x, 0, 100}], x] (* Wesley Ivan Hurt, Dec 30 2015 *)

Flatten[Table[10n + {0, 1, 4, 9}, {n, 0, 19}]] (* Alonso del Arte, Dec 30 2015 *)

Select[Range[0, 150], MemberQ[{0, 1, 4, 9}, Mod[#, 10]]&] (* Harvey P. Dale, Jul 30 2019 *)

PROG

(Magma) [(10*n-11+(-1)^n+(4+2*(-1)^n)*(-1)^((2*n-1+(-1)^n) div 4))/4: n in [1..60]]; // Vincenzo Librandi, Dec 27 2015

(PARI) is(n) = issquare(n%10); \\ Altug Alkan, Dec 29 2015

CROSSREFS

Cf. A008592, A016897, A017281, A017317, A017377, A090771, A091084, A141158, A146763, A197652.

KEYWORD

nonn,easy,base

AUTHOR

Wesley Ivan Hurt, Dec 26 2015

STATUS

approved

A262389

Numbers whose last digit is composite.

+0
3

4, 6, 8, 9, 14, 16, 18, 19, 24, 26, 28, 29, 34, 36, 38, 39, 44, 46, 48, 49, 54, 56, 58, 59, 64, 66, 68, 69, 74, 76, 78, 79, 84, 86, 88, 89, 94, 96, 98, 99, 104, 106, 108, 109, 114, 116, 118, 119, 124, 126, 128, 129, 134, 136, 138, 139, 144, 146, 148, 149

(list; graph; refs; listen; history; text; internal format)

OFFSET

1,1

COMMENTS

Numbers ending in 4, 6, 8 or 9.

Union of A017317, A017341, A017365 and A017377.

Subsequence of A118951 (numbers containing at least one composite digit).

Complement of (A197652 Union A260181).

LINKS

Table of n, a(n) for n=1..60.

Gerald Hillier and Didier Lachieze, Last Digit Composite.

Index entries for linear recurrences with constant coefficients, signature (1,0,0,1,-1).

FORMULA

G.f.: x*(4+2*x+2*x^2+x^3+x^4)/((x-1)^2*(1+x+x^2+x^3)).

a(n) = a(n-1) + a(n-4) - a(n-5) for n>5.

a(n) = (5*n+1-(-1)^n+(3+(-1)^n)*(-1)^((2*n-3-(-1)^n)/4)/2)/2.

Sum_{n>=1} (-1)^(n+1)/a(n) = (sqrt(10-2*sqrt(5))*Pi - sqrt(5)*arccoth(3/sqrt(5)) - 4*log(2))/20. - Amiram Eldar, Jul 30 2024

MAPLE

A262389:=n->(5*n+1-(-1)^n+(3+(-1)^n)*(-1)^((2*n-3-(-1)^n)/4)/2)/2: seq(A262389(n), n=1..100);

MATHEMATICA

Table[(5n+1-(-1)^n+(3+(-1)^n)*(-1)^((2n-3-(-1)^n)/4)/2)/2, {n, 100}]

LinearRecurrence[{1, 0, 0, 1, -1}, {4, 6, 8, 9, 14}, 80] (* Vincenzo Librandi, Sep 21 2015 *)

CoefficientList[Series[(4 + 2*x + 2*x^2 + x^3 + x^4)/((x - 1)^2*(1 + x + x^2 + x^3)), {x, 0, 80}], x] (* Wesley Ivan Hurt, Sep 21 2015 *)

Select[Range[200], CompositeQ[Mod[#, 10]]&] (* Requires Mathematica version 10 or later *) (* Harvey P. Dale, Jan 21 2019 *)

PROG

(Magma) [(5*n+1-(-1)^n+(3+(-1)^n)*(-1)^((2*n-3-(-1)^n) div 4) div 2) div 2: n in [1..70]]; // Vincenzo Librandi, Sep 21 2015

CROSSREFS

Cf. A017317, A017341, A017365, A017377.

Cf. A118951, A197652, A260181 (last digit is prime).

KEYWORD

nonn,base,easy

AUTHOR

Wesley Ivan Hurt, Sep 21 2015

EXTENSIONS

Name edited by Jon E. Schoenfield, Feb 15 2018

STATUS

approved

A373460

Numbers k such that k and k+1 both have an equal number of even and odd digits.

+0
2

29, 49, 69, 89, 1009, 1029, 1049, 1069, 1089, 1209, 1229, 1249, 1269, 1289, 1409, 1429, 1449, 1469, 1489, 1609, 1629, 1649, 1669, 1689, 1809, 1829, 1849, 1869, 1889, 2109, 2129, 2149, 2169, 2189, 2309, 2329, 2349, 2369, 2389, 2509, 2529, 2549, 2569, 2589, 2709

(list; graph; refs; listen; history; text; internal format)

OFFSET

1,1

COMMENTS

The terms are of the form 100*m + j, where m is either 0 or a term of A227870 and j is in {29, 49, 69, 89} if m = 0 or in {9, 29, 49, 69, 89} if m > 0.

LINKS

Amiram Eldar, Table of n, a(n) for n = 1..10000

FORMULA

a(n) = 100 * A227870(floor(n/5)) + 20 * (n mod 5) + 9, for n > 4.

EXAMPLE

29 is a term since it has one even digit (2) and one odd digit (9), and 29+1 = 30 also has one even digit (0) and one odd digit (3).

MATHEMATICA

q[n_] := Module[{d = Differences[Tally[Mod[IntegerDigits[n], 2]]]}, d != {} && d[[1, 2]] == 0]; Select[Range[3000], q[#] && q[# + 1] &]

PROG

(PARI) iseq(n) = {my(o = 0, e = 0); while(n > 0, if((n%10) % 2 == 0, e++, o++); n \= 10); e == o; }

lista(kmax) = {my(q1 = 0, q2); for(k = 1, kmax, q2 = iseq(k); if(q1 && q2, print1(k-1, ", ")); q1 = q2); }

CROSSREFS

Subsequence of A017377 and A227870.

Cf. A337238 (binary analog), A373505.

KEYWORD

nonn,base,easy

AUTHOR

Amiram Eldar, Jun 07 2024

STATUS

approved

A168419

a(n) = 9*floor(n/2).

+0
1

0, 9, 9, 18, 18, 27, 27, 36, 36, 45, 45, 54, 54, 63, 63, 72, 72, 81, 81, 90, 90, 99, 99, 108, 108, 117, 117, 126, 126, 135, 135, 144, 144, 153, 153, 162, 162, 171, 171, 180, 180, 189, 189, 198, 198, 207, 207, 216, 216, 225, 225, 234, 234, 243, 243, 252, 252, 261

(list; graph; refs; listen; history; text; internal format)

OFFSET

1,2

LINKS

Vincenzo Librandi, Table of n, a(n) for n = 1..1000

Index entries for linear recurrences with constant coefficients, signature (1,1,-1).

FORMULA

a(n) = 9*n - a(n-1) - 9, with n>1, a(1)=0.

G.f.: 9*x^2/((1+x)*(x-1)^2). - Vincenzo Librandi, Sep 19 2013

a(n) = a(n-1) +a(n-2) -a(n-3). - Vincenzo Librandi, Sep 19 2013

E.g.f.: (9/4)*(1 + (2*x - 1)*exp(2*x))*exp(-x). - G. C. Greubel, Jul 22 2016

MATHEMATICA

Table[9 Floor[n/2], {n, 70}] (* or *) CoefficientList[Series[9 x/((1 + x) (x - 1)^2), {x, 0, 70}], x] (* Vincenzo Librandi, Sep 19 2013 *)

LinearRecurrence[{1, 1, -1}, {0, 9, 9}, 60] (* Harvey P. Dale, Apr 21 2019 *)

PROG

(Magma) [9*Floor(n/2): n in [1..70]]; // Vincenzo Librandi, Sep 19 2013

CROSSREFS

Cf. A004526, A017377.

KEYWORD

nonn,easy

AUTHOR

Vincenzo Librandi, Nov 25 2009

EXTENSIONS

New definition by Vincenzo Librandi, Sep 19 2013

STATUS

approved

A346950

Positive integers k that are the product of two integers ending with 3.

+0
11

9, 39, 69, 99, 129, 159, 169, 189, 219, 249, 279, 299, 309, 339, 369, 399, 429, 459, 489, 519, 529, 549, 559, 579, 609, 639, 669, 689, 699, 729, 759, 789, 819, 849, 879, 909, 939, 949, 969, 989, 999, 1029, 1059, 1079, 1089, 1119, 1149, 1179, 1209, 1219, 1239, 1269

(list; graph; refs; listen; history; text; internal format)

OFFSET

1,1

COMMENTS

All the terms end with 9 (A017377).

LINKS

Stefano Spezia, Table of n, a(n) for n = 1..10000

FORMULA

Limit_{n->oo} a(n)/a(n-1) = 1.

EXAMPLE

9 = 3*3, 39 = 3*13, 69 = 3*23, 99 = 3*33, 129 = 3*43, 159 = 3*53, 169 = 13*13, 189 = 3*63, ...

MATHEMATICA

a={}; For[n=0, n<=250, n++, For[k=0, k<=n, k++, If[Mod[10*n+9, 10*k+3]==0 && Mod[(10*n+9)/(10*k+3), 10]==3&& 10*n+9>Max[a], AppendTo[a, 10*n+9]]]]; a

PROG

(Python)

def aupto(lim): return sorted(set(a*b for a in range(3, lim//3+1, 10) for b in range(a, lim//a+1, 10)))

print(aupto(1270)) # Michael S. Branicky, Aug 08 2021

CROSSREFS

Cf. A017377 (supersequence), A053742 (ending with 5), A139245 (ending with 2), A324297 (ending with 6), A346951, A346952, A346953.

KEYWORD

nonn,base

AUTHOR

Stefano Spezia, Aug 08 2021

STATUS

approved

A135705

a(n) = 10*binomial(n,2) + 9*n.

+0
14

0, 9, 28, 57, 96, 145, 204, 273, 352, 441, 540, 649, 768, 897, 1036, 1185, 1344, 1513, 1692, 1881, 2080, 2289, 2508, 2737, 2976, 3225, 3484, 3753, 4032, 4321, 4620, 4929, 5248, 5577, 5916, 6265, 6624, 6993, 7372, 7761, 8160, 8569, 8988, 9417, 9856, 10305, 10764

(list; graph; refs; listen; history; text; internal format)

OFFSET

0,2

COMMENTS

Also, second 12-gonal (or dodecagonal) numbers. Identity for the numbers b(n)=n*(h*n+h-2)/2 (see Crossrefs): Sum_{i=0..n} (b(n)+i)^2 = (Sum_{i=n+1..2*n} (b(n)+i)^2) + h*(h-4)*A000217(n)^2 for n>0. - Bruno Berselli, Jan 15 2011

Sequence found by reading the line from 0, in the direction 0, 28, ..., and the line from 9, in the direction 9, 57, ..., in the square spiral whose vertices are the generalized 12-gonal numbers A195162. - Omar E. Pol, Jul 24 2012

Bisection of A195162. - Omar E. Pol, Aug 04 2012

LINKS

Ivan Panchenko, Table of n, a(n) for n = 0..1000

L. Hogben, Choice and Chance by Cardpack and Chessboard, Vol. 1, Max Parrish and Co, London, 1950, p. 36.

Leo Tavares, Illustration: Diamond Clipped Stars

Index entries for linear recurrences with constant coefficients, signature (3,-3,1).

FORMULA

From R. J. Mathar, Mar 06 2008: (Start)

O.g.f.: x*(9+x)/(1-x)^3.

a(n) = n*(5*n+4). (End)

a(n) = a(n-1) + 10*n - 1 (with a(0)=0). - Vincenzo Librandi, Nov 24 2009

a(n) = Sum_{i=0..n-1} A017377(i) for n>0. - Bruno Berselli, Jan 15 2011

a(n) = A131242(10n+8). - Philippe Deléham, Mar 27 2013

Sum_{n>=1} 1/a(n) = 5/16 + sqrt(1 + 2/sqrt(5))*Pi/8 - 5*log(5)/16 - sqrt(5)*log((1 + sqrt(5))/2)/8 = 0.2155517745488486003038... . - Vaclav Kotesovec, Apr 27 2016

From G. C. Greubel, Oct 29 2016: (Start)

a(n) = 3*a(n-1) - 3*a(n-2) + a(n-3).

E.g.f.: x*(9 + 5*x)*exp(x). (End)

a(n) = A003154(n+1) - A000290(n+1). - Leo Tavares, Mar 29 2022

MATHEMATICA

LinearRecurrence[{3, -3, 1}, {0, 9, 28}, 50] (* or *) Table[5*n^2 + 4*n, {n, 0, 50}] (* G. C. Greubel, Oct 29 2016 *)

Table[10 Binomial[n, 2]+9n, {n, 0, 60}] (* Harvey P. Dale, Jun 14 2023 *)

PROG

(PARI) a(n) = 10*binomial(n, 2) + 9*n \\ Charles R Greathouse IV, Jun 11 2015

(Magma) [n*(5*n+4): n in [0..50]]; // G. C. Greubel, Jul 04 2019

(Sage) [n*(5*n+4) for n in (0..50)] # G. C. Greubel, Jul 04 2019

(GAP) List([0..50], n-> n*(5*n+4)) # G. C. Greubel, Jul 04 2019

CROSSREFS

Second n-gonal numbers: A005449, A014105, A147875, A045944, A179986, A033954, A062728, this sequence.

Cf. A003154, A000290.

Cf. A195162.

KEYWORD

nonn,easy

AUTHOR

N. J. A. Sloane, Mar 04 2008

STATUS

approved

A273669

Decimal representation ends with either 2 or 9.

+0
15

2, 9, 12, 19, 22, 29, 32, 39, 42, 49, 52, 59, 62, 69, 72, 79, 82, 89, 92, 99, 102, 109, 112, 119, 122, 129, 132, 139, 142, 149, 152, 159, 162, 169, 172, 179, 182, 189, 192, 199, 202, 209, 212, 219, 222, 229, 232, 239, 242, 249, 252, 259, 262, 269, 272, 279, 282, 289, 292, 299, 302, 309, 312, 319, 322, 329, 332, 339

(list; graph; refs; listen; history; text; internal format)

OFFSET

1,1

COMMENTS

Natural numbers not in A273664.

LINKS

Antti Karttunen, Table of n, a(n) for n = 1..10000

Index entries for linear recurrences with constant coefficients, signature(1,1,-1).

FORMULA

a(n) = 10*(((n-2)+A000035(n))/2) + 2 [when n is odd], or + 9 [when n is even].

For n >= 5, a(n) = 2*a(n-2) - a(n-4).

a(n) = A126760(A084967(n)).

a(n) = A249746((3*A249745(n))-1).

Other identities. For all n >= 1:

A084967(n) = 5*A007310(n) = A007310(a(n)).

G.f.: x*(x^2+7*x+2)/((x+1)*(x-1)^2).

Sum_{n>=1} (-1)^(n+1)/a(n) = sqrt((1+1/sqrt(5))/2)*phi^2*Pi/10 - log(phi)/(2*sqrt(5)) - log(2)/5, where phi is the golden ratio (A001622). - Amiram Eldar, Apr 15 2023

MATHEMATICA

Select[Range@ 340, MemberQ[{2, 9}, Mod[#, 10]] &] (* or *)

Table[{10 n + 2, 10 n + 9}, {n, 0, 33}] // Flatten (* or *)

CoefficientList[Series[(-5/(1 - x) + (11 - x)/(-1 + x)^2 - 2/(1 + x))/2, {x, 0, 67}], x] (* Michael De Vlieger, Aug 07 2016 *)

PROG

(Scheme)

(define (A273669 n) (+ (* 10 (/ (+ (- n 2) (if (odd? n) 1 0)) 2)) (if (odd? n) 2 9)))

CROSSREFS

Sequences A017293 and A017377 interleaved.

Cf. A000035, A001622, A007310, A084967, A126760, A249745, A249746.

Cf. also A273664, A249824, A275716.

KEYWORD

nonn,base,easy

AUTHOR

Antti Karttunen, Aug 06 2016

STATUS

approved

A190876

Numbers 1 through 8 together with numbers congruent to 9 mod 10.

+0
2

1, 2, 3, 4, 5, 6, 7, 8, 9, 19, 29, 39, 49, 59, 69, 79, 89, 99, 109, 119, 129, 139, 149, 159, 169, 179, 189, 199, 209, 219, 229, 239, 249, 259, 269, 279, 289, 299, 309, 319, 329, 339, 349, 359, 369, 379, 389, 399, 409, 419, 429, 439, 449, 459, 469, 479, 489, 499, 509, 519, 529, 539, 549, 559, 569, 579, 589, 599, 609

(list; graph; refs; listen; history; text; internal format)

OFFSET

1,2

COMMENTS

In lunar arithmetic, numbers n with the property that the sum of the divisors of n that are <= n is equal to n.

LINKS

Vincenzo Librandi, Table of n, a(n) for n = 1..1000

D. Applegate, M. LeBrun and N. J. A. Sloane, Dismal Arithmetic [Note: we have now changed the name from "dismal arithmetic" to "lunar arithmetic" - the old name was too depressing]

Index entries for sequences related to dismal (or lunar) arithmetic

Index entries for linear recurrences with constant coefficients, signature (2,-1).

FORMULA

G.f.: x*(1+9*x^9)/(1-x)^2. - Bruno Berselli, May 23 2011

a(n) = 2*a(n-1) -a(n-2). - Vincenzo Librandi, Jul 12 2012

PROG

(Maxima) makelist(if n<9 then n else 10*n-81, n, 1, 70); /* Bruno Berselli, May 24 2011 */

(Magma) [n lt 9 select n else 10*n-81: n in [1..70]]; // Bruno Berselli, May 24 2011

CROSSREFS

Cf. A017377.

KEYWORD

nonn,base

AUTHOR

N. J. A. Sloane, May 23 2011

STATUS

approved