A027327 a(n) = Sum_{k=0..m} (k+1) * A026120(n, m-k), where m=0 for n=0,1; m=n for n >= 2.

1, 3, 12, 36, 108, 324, 972, 2916, 8748, 26244, 78732, 236196, 708588, 2125764, 6377292, 19131876, 57395628, 172186884, 516560652, 1549681956, 4649045868, 13947137604, 41841412812, 125524238436, 376572715308

Offset: 0

Author

Clark Kimberling

Keywords

• nonn

Links

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

Programs

Mathematica

Join[{1,3},NestList[3#&,12,30]] (* Harvey P. Dale, Aug 13 2024 *)

Formula

G.f.: (1+3x^2)/(1-3x). - Paul Barry, May 19 2003

a(n) = A003946(n), n>1. - R. J. Mathar, Oct 23 2008