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E.g.f.: exp(-Sum_{n>=1} sigma(n) * x^n).
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%I #14 Aug 17 2021 10:10:55

%S 1,-1,-5,-7,1,839,4171,54305,102817,-4303441,-74521349,-1595325271,

%T -20768141855,-222701825737,1485790534411,65580347824529,

%U 2880129557707201,67631429234674655,1543424936566399867,23542870556917468889,119940955037901088321

%N E.g.f.: exp(-Sum_{n>=1} sigma(n) * x^n).

%H Seiichi Manyama, <a href="/A294403/b294403.txt">Table of n, a(n) for n = 0..439</a>

%F a(0) = 1 and a(n) = (-1) * (n-1)! * Sum_{k=1..n} k*A000203(k)*a(n-k)/(n-k)! for n > 0.

%F E.g.f.: Product_{k>=1} (1 - x^k)^f(k), where f(k) = (1/k) * Sum_{j=1..k} gcd(k,j)^2. - _Ilya Gutkovskiy_, Aug 17 2021

%o (PARI) N=66; x='x+O('x^N); Vec(serlaplace(exp(-sum(k=1, N, sigma(k)*x^k))))

%Y E.g.f.: exp(-Sum_{n>=1} sigma_k(n) * x^n): A294402 (k=0), this sequence (k=1), A294404 (k=2).

%Y Cf. A000203, A010815, A069097, A294361.

%K sign

%O 0,3

%A _Seiichi Manyama_, Oct 30 2017