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A174465
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G.f.: exp( Sum_{n>=1} A174466(n)*x^n/n ) where A174466(n) = Sum_{d|n} d*sigma(n/d)*tau(d).
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2
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1, 1, 4, 7, 19, 31, 74, 122, 258, 430, 835, 1378, 2557, 4162, 7382, 11932, 20471, 32676, 54634, 86251, 141001, 220371, 353413, 546783, 863043, 1322425, 2057525, 3125092, 4801297, 7230393, 10984924, 16410474, 24679719, 36593278, 54526145, 80272501
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OFFSET
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0,3
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COMMENTS
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Compare to the g.f. of the number of planar partitions of n (A000219):
exp( Sum_{n>=1} sigma_2(n)*x^n/n ) where sigma_2(n) = Sum_{d|n} d*sigma(n/d)*phi(d).
tau(n) = A000005(n) = the number of divisors of n,
and sigma(n) = A000203(n) = sum of divisors of n.
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LINKS
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Table of n, a(n) for n=0..35.
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PROG
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(PARI) {a(n)=polcoeff(exp(sum(m=1, n, x^m/m*sumdiv(m, d, d*sigma(m/d)*sigma(d, 0)))+x*O(x^n)), n)}
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CROSSREFS
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Cf. A174466, A000203 (sigma), A000005 (tau).
Sequence in context: A063605 A024824 A164265 * A006381 A102991 A062306
Adjacent sequences: A174462 A174463 A174464 * A174466 A174467 A174468
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KEYWORD
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nonn
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AUTHOR
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Paul D. Hanna, Apr 04 2010
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STATUS
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approved
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