A339686 a(n) = Sum_{d|n} 6^(d-1).

1, 7, 37, 223, 1297, 7819, 46657, 280159, 1679653, 10078999, 60466177, 362805091, 2176782337, 13060740679, 78364165429, 470185264735, 2821109907457, 16926661132171, 101559956668417, 609359750089711, 3656158440109669, 21936950700844039, 131621703842267137

Offset

1,2

Links

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

Formula

G.f.: Sum_{k>=1} x^k / (1 - 6*x^k).

G.f.: Sum_{k>=1} 6^(k-1) * x^k / (1 - x^k).

a(n) ~ 6^(n-1). - Vaclav Kotesovec, Jun 05 2021

Mathematica

Table[Sum[6^(d - 1), {d, Divisors[n]}], {n, 1, 23}]
nmax = 23; CoefficientList[Series[Sum[x^k/(1 - 6 x^k), {k, 1, nmax}], {x, 0, nmax}], x] // Rest

Prog

(PARI) a(n) = sumdiv(n, d, 6^(d-1)); \\ Michel Marcus, Dec 13 2020

Crossrefs

Column 6 of A308813.

Cf. A000400, A034729, A034730, A113999, A320071, A339684, A339685, A339687, A339688, A339689.

Sequence in context: A046235 A297329 A347726 * A144496 A025012 A039938

Adjacent sequences: A339683 A339684 A339685 * A339687 A339688 A339689

Keyword

nonn

Author

Ilya Gutkovskiy, Dec 12 2020

Status

approved