OFFSET
0,2
LINKS
Harvey P. Dale, Table of n, a(n) for n = 0..1000
Index entries for linear recurrences with constant coefficients, signature (3,-3,1).
FORMULA
G.f.: 3*x*(7+5*x)/(1-x)^3. - Vincenzo Librandi, Dec 18 2014
From Wesley Ivan Hurt, Dec 16 2015: (Start)
a(n) = 3*a(n-1) - 3*a(n-2) + a(n-3) for n>2.
a(n) = 3 * A049453(n). (End)
E.g.f.: 3*exp(x)*x*(7 + 6*x). - Stefano Spezia, Jun 29 2021
MAPLE
MATHEMATICA
Table[3n(6n+1), {n, 0, 40}] (* or *) LinearRecurrence[{3, -3, 1}, {0, 21, 78}, 40] (* Harvey P. Dale, Dec 17 2014 *)
CoefficientList[Series[x (21 + 15 x) / (1 - x)^3, {x, 0, 50}], x] (* Vincenzo Librandi, Dec 18 2014 *)
PROG
(Magma) [18*n^2+3*n: n in [0..50]]; // Vincenzo Librandi, Dec 18 2014
(PARI) a(n)=3*n*(6*n+1) \\ Charles R Greathouse IV, Oct 07 2015
CROSSREFS
KEYWORD
nonn,easy
AUTHOR
Reinhard Zumkeller, Sep 17 2008
STATUS
approved