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A339686 a(n) = Sum_{d|n} 6^(d-1). 8
1, 7, 37, 223, 1297, 7819, 46657, 280159, 1679653, 10078999, 60466177, 362805091, 2176782337, 13060740679, 78364165429, 470185264735, 2821109907457, 16926661132171, 101559956668417, 609359750089711, 3656158440109669, 21936950700844039, 131621703842267137 (list; graph; refs; listen; history; text; internal format)
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).

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: A077239 A046235 A297329 * A144496 A025012 A039938

Adjacent sequences:  A339683 A339684 A339685 * A339687 A339688 A339689

KEYWORD

nonn

AUTHOR

Ilya Gutkovskiy, Dec 12 2020

STATUS

approved

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Last modified May 14 18:54 EDT 2021. Contains 343900 sequences. (Running on oeis4.)