A015490 a(0)=1, a(1)=5, a(n) = sum_{k=0}^{k=n-1} 5^k a(k).

1, 5, 26, 676, 85176, 53320176, 166678870176, 2604524025370176, 203481044006070370176, 79484986295915244420370176, 155244193344195757673779920370176, 1516056730871105040228764708644920370176

Offset

0,2

Links

Table of n, a(n) for n=0..11.

Formula

a(n) = (5^(n-2) + 1) * a(n-1). - Vincenzo Librandi, Nov 11 2012

Prog

(Magma) I:=[1, 5, 26]; [n le 3 select I[n] else (5^(n-2)+1)*Self(n-1): n in [1..15]]; // Vincenzo Librandi, Nov 11 2012

Crossrefs

Sequence in context: A156217 A156216 A320987 * A118366 A226125 A132509

Adjacent sequences: A015487 A015488 A015489 * A015491 A015492 A015493

Keyword

nonn,easy

Author

Olivier Gérard

Status

approved