A153786 6 times heptagonal numbers: a(n) = 3*n*(5*n-3).
0, 6, 42, 108, 204, 330, 486, 672, 888, 1134, 1410, 1716, 2052, 2418, 2814, 3240, 3696, 4182, 4698, 5244, 5820, 6426, 7062, 7728, 8424, 9150, 9906, 10692, 11508, 12354, 13230, 14136, 15072, 16038, 17034, 18060, 19116, 20202, 21318
Offset: 0
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).
Programs
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Mathematica
s=0;lst={s};Do[s+=n;AppendTo[lst,s],{n,6,8!,30}];lst (* Vladimir Joseph Stephan Orlovsky, Apr 03 2009 *) Table[ 3*n*(5*n-3), {n,0,25}] (* or *) LinearRecurrence[{3,-3,1},{0,6,42}, 25] (* G. C. Greubel, Aug 28 2016 *) -
PARI
a(n) = 3*n*(5*n-3); \\ Michel Marcus, Aug 28 2016
Formula
a(n) = 30*n + a(n-1) - 24 for n>0, a(0)=0. - Vincenzo Librandi, Aug 03 2010
From G. C. Greubel, Aug 28 2016: (Start)
a(n) = 3*a(n-1) - 3*a(n-2) + a(n-3).
G.f.: 6*x*(1 + 4*x)/(1 - x)^3.
E.g.f.: 3*x*(2 + 5*x)*exp(x). (End)