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%I #4 Sep 17 2018 15:42:52
%S 1,1,3,14,136,2411,88903,6309849,866470849,240522266760,
%T 132000248840652,141226630324344532,306101744973083495408,
%U 1327520858367342045830198,11328405846086223895036194126,196814026990537767059856457640779,6894163531963490274906095710739747873
%N a(n) = [x^n] exp(Sum_{k>=1} sigma_n(k)*x^k/k).
%F a(n) = [x^n] Product_{k>=1} 1/(1 - x^k)^(k^(n-1)).
%t Table[SeriesCoefficient[Exp[Sum[DivisorSigma[n, k] x^k/k, {k, 1, n}]], {x, 0, n}], {n, 0, 16}]
%t Table[SeriesCoefficient[Product[1/(1 - x^k)^(k^(n - 1)), {k, 1, n}], {x, 0, n}], {n, 0, 16}]
%Y Diagonal of A144048.
%Y Cf. A252782, A305207.
%K nonn
%O 0,3
%A _Ilya Gutkovskiy_, Sep 17 2018
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