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 A056121 a(n) = n*(n + 15)/2. 14
 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 G. C. Greubel, Table of n, a(n) for n = 0..1000 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) = binomial(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) = a(n-1)+ n + 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 E.g.f.: x*(16 + x)*exp(x)/2. - G. C. Greubel, Jan 18 2020 MAPLE a:=n->n*(n+15)/2: seq(a(n), n=0..60); MATHEMATICA ((2*Range[0, 60] +15)^2 -15^2)/8 (* G. C. Greubel, Jan 18 2020 *) PROG (PARI) a(n)=n*(n+15)/2 \\ Charles R Greathouse IV, Sep 24 2015 (MAGMA) [n*(n+15)/2: n in [0..60]]; // G. C. Greubel, Jan 18 2020 (Sage) [n*(n+15)/2 for n in (0..60)] # G. C. Greubel, Jan 18 2020 (GAP) List([0..60], n-> n*(n+15)/2 ); # G. C. Greubel, Jan 18 2020 CROSSREFS Cf. A000096, A001477, A056000, A056119, A056126. Sequence in context: A044441 A189381 A190749 * A264355 A028884 A322473 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 February 16 21:37 EST 2020. Contains 331975 sequences. (Running on oeis4.)