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A308672 a(n) = Sum_{d|n} d^(d^3). 1
1, 257, 7625597484988, 340282366920938463463374607431768211713, 2350988701644575015937473074444491355637331113544175043017503412556834518909454345703126 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,2

COMMENTS

The next term (a(6)) has 169 digits. - Harvey P. Dale, Sep 08 2020

LINKS

Table of n, a(n) for n=1..5.

FORMULA

L.g.f.: -log(Product_{k>=1} (1 - x^k)^(k^(k^3-1))) = Sum_{k>=1} a(k)*x^k/k.

MATHEMATICA

Table[Total[Divisors[n]^Divisors[n]^3], {n, 5}] (* Harvey P. Dale, Sep 08 2020 *)

a[n_] := DivisorSum[n, #^(#^3) &]; Array[a, 5] (* Amiram Eldar, May 11 2021 *)

PROG

(PARI) {a(n) = sumdiv(n, d, d^d^3)}

(PARI) N=10; x='x+O('x^N); Vec(x*deriv(-log(prod(k=1, N, (1-x^k)^(k^(k^3-1))))))

CROSSREFS

Column k=3 of A308674.

Cf. A000005, A062796, A308671.

Sequence in context: A275098 A194155 A238614 * A308675 A121237 A161683

Adjacent sequences:  A308669 A308670 A308671 * A308673 A308674 A308675

KEYWORD

nonn

AUTHOR

Seiichi Manyama, Jun 16 2019

STATUS

approved

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Last modified September 24 20:43 EDT 2021. Contains 347651 sequences. (Running on oeis4.)