A061983 a(n) = 3^n - (3*n^2 + n + 2)/2.

0, 0, 1, 11, 54, 202, 671, 2109, 6460, 19556, 58893, 176959, 531218, 1594062, 4782667, 14348561, 43046328, 129139720, 387419993, 1162260915, 3486783790, 10460352530, 31381058871, 94143178021, 282429535604, 847288608492, 2541865827301, 7625597483879, 22876792453770

Offset: 0

Author

Henry Bottomley, May 24 2001

Keywords

• nonn

Links

• Harry J. Smith, Table of n, a(n) for n = 0..200
• Index entries for linear recurrences with constant coefficients, signature (6,-12,10,-3).

Crossrefs

Column of A061980.

Programs

PARI

a(n) = { 3^n - (3*n^2 + n + 2)/2 } \\ Harry J. Smith, Jul 29 2009

Formula

G.f.: x^2*(1 + 5*x)/((1 - x)^3*(1 - 3*x)). - Andrew Howroyd, Dec 28 2024