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A318814 Expansion of e.g.f. Product_{k>=1} ((1 + x^k)/(1 - x^k))^(sigma(k)/k). 6
1, 2, 10, 64, 512, 4768, 53056, 645440, 8868352, 133302016, 2184149504, 38530160128, 733246566400, 14834910150656, 319778313883648, 7292507623063552, 175517505539538944, 4440588163825008640, 117969026857318678528, 3276703253565946855424, 95086071773832697348096 (list; graph; refs; listen; history; text; internal format)
OFFSET
0,2
COMMENTS
Convolution of A305127 and A318769.
LINKS
FORMULA
log(a(n)/n!) ~ Pi^2 * sqrt(n/6).
MAPLE
seq(n!*coeff(series(mul(((1+x^k)/(1-x^k))^(sigma(k)/k), k=1..100), x=0, 21), x, n), n=0..20); # Paolo P. Lava, Jan 09 2019
MATHEMATICA
nmax = 20; CoefficientList[Series[Product[((1+x^k)/(1-x^k))^(DivisorSigma[1, k]/k), {k, 1, nmax}], {x, 0, nmax}], x] * Range[0, nmax]!
CROSSREFS
Sequence in context: A223127 A361407 A323666 * A130721 A167449 A064170
KEYWORD
nonn
AUTHOR
Vaclav Kotesovec, Sep 04 2018
STATUS
approved

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Last modified February 27 04:33 EST 2024. Contains 370362 sequences. (Running on oeis4.)