A339685 a(n) = Sum_{d|n} 5^(d-1).

1, 6, 26, 131, 626, 3156, 15626, 78256, 390651, 1953756, 9765626, 48831406, 244140626, 1220718756, 6103516276, 30517656381, 152587890626, 762939846906, 3814697265626, 19073488282006, 95367431656276, 476837167968756, 2384185791015626, 11920929003987656

Offset

1,2

Links

Seiichi Manyama, Table of n, a(n) for n = 1..1000

Formula

G.f.: Sum_{k>=1} x^k / (1 - 5*x^k).

G.f.: Sum_{k>=1} 5^(k-1) * x^k / (1 - x^k).

a(n) ~ 5^(n-1). - Vaclav Kotesovec, Jun 05 2021

Mathematica

Table[Sum[5^(d - 1), {d, Divisors[n]}], {n, 1, 24}]
nmax = 24; CoefficientList[Series[Sum[x^k/(1 - 5 x^k), {k, 1, nmax}], {x, 0, nmax}], x] // Rest

Prog

(PARI) a(n) = sumdiv(n, d, 5^(d-1)); \\ Michel Marcus, Dec 13 2020

Crossrefs

Column 5 of A308813.

Cf. A000351, A034729, A034730, A113999, A295506, A339684, A339686, A339687, A339688, A339689.

Sequence in context: A298625 A046233 A140231 * A364744 A144037 A187458

Adjacent sequences: A339682 A339683 A339684 * A339686 A339687 A339688

Keyword

nonn

Author

Ilya Gutkovskiy, Dec 12 2020

Status

approved