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A056121 a(n) = n*(n+15)/2. 12
0, 8, 17, 27, 38, 50, 63, 77, 92, 108, 125, 143, 162, 182, 203, 225, 248, 272, 297, 323, 350, 378, 407, 437, 468, 500, 533, 567, 602, 638, 675, 713, 752, 792, 833, 875, 918, 962, 1007, 1053, 1100, 1148, 1197, 1247, 1298, 1350, 1403, 1457, 1512, 1568, 1625 (list; graph; refs; listen; history; text; internal format)
OFFSET

0,2

LINKS

Table of n, a(n) for n=0..50.

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

FORMULA

G.f.: x*(8-7*x)/(1-x)^3.

a(n) = A000096(n) + 6*n = A056119(n) + n = A056126(n) - n. - Zerinvary Lajos, Oct 01 2006

a(n-15) = C(n,2) - 7*n. - Zerinvary Lajos, Nov 26 2006

a(n) = A126890(n,7) for n>6. - Reinhard Zumkeller, Dec 30 2006

Let f(n,i,a) = sum_{k=0..n-i} binomial(n,k)*stirling1(n-k,i)*product_{j=0..k-1} (-a-j), then a(n) = -f(n,n-1,8), for n>=1. - Milan Janjic, Dec 20 2008

a(n) = n + a(n-1) + 7 (with a(0)=0). - Vincenzo Librandi, Aug 07 2010

sum_{n>=1} 1/a(n) = 1195757/2702700 via A132760. - R. J. Mathar, Jul 14 2012

a(n) = 8*n - floor(n/2) + floor(n^2/2). - Wesley Ivan Hurt, Jun 15 2013

MAPLE

a:=n->n*(n+15)/2: seq(a(n), n=0..66);

MATHEMATICA

i=-7; s=0; lst={}; Do[s+=n+i; If[s>=0, AppendTo[lst, s]], {n, 0, 6!, 1}]; lst (* Vladimir Joseph Stephan Orlovsky, Oct 29 2008 *)

PROG

(PARI) a(n)=n*(n+15)/2 \\ Charles R Greathouse IV, Sep 24 2015

CROSSREFS

Cf. A000096, A056119, A056126, A056000, A001477.

Sequence in context: A044441 A189381 A190749 * A264355 A028884 A247117

Adjacent sequences:  A056118 A056119 A056120 * A056122 A056123 A056124

KEYWORD

easy,nonn

AUTHOR

Barry E. Williams, Jul 06 2000

EXTENSIONS

More terms from James A. Sellers, Jul 07 2000

STATUS

approved

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Last modified November 21 16:08 EST 2017. Contains 295003 sequences.