A027107 a(n) = Sum_{k=0..2n} (k+1) * A027082(n, 2n-k).

1, 6, 20, 62, 188, 566, 1700, 5102, 15308, 45926, 137780, 413342, 1240028, 3720086, 11160260, 33480782, 100442348, 301327046, 903981140, 2711943422, 8135830268, 24407490806, 73222472420, 219667417262, 659002251788

Offset: 0

Author

Clark Kimberling

Keywords

• nonn
• easy

Links

• Vincenzo Librandi, Table of n, a(n) for n = 0..1000
• Index entries for linear recurrences with constant coefficients, signature (4,-3).

Programs

Magma

[1] cat [7*3^n-1: n in [0..30]]; // Vincenzo Librandi, Mar 24 2013

Mathematica

Join[{1}, Table[7 3^(n-1) - 1, {n, 30}]] (* Vincenzo Librandi, Mar 24 2013 *)

Formula

For n>0, a(n) = 7*3^(n-1) - 1.

G.f.: (1+2*x-x^2)/(1-4*x+3*x^2). [Bruno Berselli, Mar 25 2013]

a(n) = 2*A237930(n-1), n>0. - R. J. Mathar, Jun 24 2020