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A174465 G.f.: exp( Sum_{n>=1} A174466(n)*x^n/n ) where A174466(n) = Sum_{d|n} d*sigma(n/d)*tau(d). 2
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 (list; graph; refs; listen; history; text; internal format)
OFFSET

0,3

COMMENTS

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.

LINKS

Table of n, a(n) for n=0..35.

PROG

(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)}

CROSSREFS

Cf. A174466, A000203 (sigma), A000005 (tau).

Sequence in context: A063605 A024824 A164265 * A006381 A274691 A102991

Adjacent sequences:  A174462 A174463 A174464 * A174466 A174467 A174468

KEYWORD

nonn

AUTHOR

Paul D. Hanna, Apr 04 2010

STATUS

approved

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Last modified December 7 19:05 EST 2016. Contains 278895 sequences.