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A308756 a(n) = Sum_{d|n} d^(2*(d-2)). 3
1, 2, 10, 258, 15626, 1679627, 282475250, 68719476994, 22876792454971, 10000000000015627, 5559917313492231482, 3833759992447476802059, 3211838877954855105157370, 3214199700417740937033562867, 3787675244106352329254150406260 (list; graph; refs; listen; history; text; internal format)
OFFSET
1,2
LINKS
FORMULA
L.g.f.: -log(Product_{k>=1} (1 - x^k)^(k^(2*k-5))) = Sum_{k>=1} a(k)*x^k/k.
G.f.: Sum_{k>=1} k^(2*(k-2)) * x^k/(1 - x^k).
MATHEMATICA
a[n_] := DivisorSum[n, #^(2*(# - 2)) &]; Array[a, 15] (* Amiram Eldar, May 08 2021 *)
PROG
(PARI) {a(n) = sumdiv(n, d, d^(2*(d-2)))}
(PARI) N=20; x='x+O('x^N); Vec(x*deriv(-log(prod(k=1, N, (1-x^k)^k^(2*k-5)))))
(PARI) N=20; x='x+O('x^N); Vec(sum(k=1, N, k^(2*(k-2))*x^k/(1-x^k)))
CROSSREFS
Sequence in context: A289948 A282567 A360945 * A225371 A088310 A134473
KEYWORD
nonn
AUTHOR
Seiichi Manyama, Jun 22 2019
STATUS
approved

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Last modified March 28 05:02 EDT 2024. Contains 371235 sequences. (Running on oeis4.)