A015487 a(0)=1, a(1)=3, a(n) = sum_{k=0}^{k=n-1} 3^k a(k).

1, 3, 10, 100, 2800, 229600, 56022400, 40896352000, 89481218176000, 587175753670912000, 11557967535258231808000, 682497982956998588262400000, 120903152684866385913507635200000

Offset

0,2

Links

Table of n, a(n) for n=0..12.

Formula

a(n) = (3^(n-2) + 1) * a(n-1). - Vincenzo Librandi, Nov 10 2012

Prog

(Magma) I:=[1, 3, 10]; [n le 3 select I[n] else (3^(n-2)+1)*Self(n-1): n in [1..15]]; // Vincenzo Librandi, Nov 10 2012

Crossrefs

Sequence in context: A013262 A013267 A013268 * A326428 A260813 A062013

Adjacent sequences: A015484 A015485 A015486 * A015488 A015489 A015490

Keyword

nonn,easy

Author

Olivier Gérard

Status

approved