A051406 a(n) = (3^n+1) * (3^(n+1)+1) / 8.

1, 5, 35, 287, 2501, 22265, 199655, 1794707, 16145801, 145292525, 1307573675, 11767985927, 105911341901, 953200482785, 8578799562095, 77209181709947, 694882592342801, 6253943201945045, 56285488430084915, 506569394708502767, 4559124548889740501

Offset

0,2

Links

Colin Barker, Table of n, a(n) for n = 0..1000

Index entries for linear recurrences with constant coefficients, signature (13,-39,27).

Formula

a(n) = 13*a(n-1) - 39*a(n-2) + 27*a(n-3). G.f.: -(1-8*x+9*x^2)/((x-1)*(3*x-1)*(9*x-1)). [R. J. Mathar, Jul 25 2009]

Prog

(PARI) Vec((1 - 8*x + 9*x^2) / ((1 - x)*(1 - 3*x)*(1 - 9*x)) + O(x^30)) \\ Colin Barker, Jul 16 2017

Crossrefs

Sequence in context: A369157 A002294 A369128 * A000356 A370844 A027392

Adjacent sequences: A051403 A051404 A051405 * A051407 A051408 A051409

Keyword

nonn,easy

Author

Colin Mallows

Status

approved