A320238 G.f.: Product_{k>=1, j>=1} (1 + x^(k*j)) / (1 - x^(k*j))^2.

1, 3, 11, 31, 85, 209, 504, 1138, 2514, 5339, 11098, 22432, 44535, 86523, 165496, 311187, 577190, 1055524, 1907423, 3405574, 6016826, 10520065, 18222215, 31275320, 53230224, 89860112, 150551503, 250388180, 413572707, 678574627, 1106396434, 1793009335

Offset

0,2

Comments

Convolution of A107742 and A320236.

Links

Vaclav Kotesovec, Table of n, a(n) for n = 0..10000

Formula

Conjecture: log(a(n)) ~ Pi * sqrt(5*n*log(n)/6).

Mathematica

nmax = 50; CoefficientList[Series[Product[(1+x^(k*j))/(1-x^(k*j))^2, {k, 1, nmax}, {j, 1, Floor[nmax/k] + 1}], {x, 0, nmax}], x]

Crossrefs

Cf. A158441, A107742, A320236.

Sequence in context: A268800 A054343 A369442 * A369399 A108898 A291887

Adjacent sequences: A320235 A320236 A320237 * A320239 A320240 A320241

Keyword

nonn

Author

Vaclav Kotesovec, Oct 08 2018

Status

approved