A015495 a(0)=1, a(1)=7, a(n) = sum_{k=0}^{k=n-1} 7^k a(k).

1, 7, 50, 2500, 860000, 2065720000, 34720621760000, 4084881150064000000, 3364079361848306816000000, 19393251433341842829490432000000, 782587666186514855538867732678656000000

Offset

0,2

Links

Table of n, a(n) for n=0..10.

Formula

a(n) = (7^(n-2) + 1) * Self(n-1). - Vincenzo Librandi, Nov 11 2012

Prog

(Magma) I:=[1, 7, 50]; [n le 3 select I[n] else (7^(n-2)+1)*Self(n-1): n in [1..15]]; // Vincenzo Librandi, Nov 11 2012

Crossrefs

Sequence in context: A041086 A197890 A320989 * A056581 A039308 A029525

Adjacent sequences: A015492 A015493 A015494 * A015496 A015497 A015498

Keyword

nonn,easy

Author

Olivier Gérard

Status

approved