A320236 G.f.: Product_{k>=1, j>=1} 1/(1 - x^(k*j))^2.

1, 2, 7, 16, 41, 86, 193, 384, 787, 1504, 2899, 5338, 9852, 17586, 31330, 54490, 94350, 160370, 271171, 451776, 748460, 1225106, 1993860, 3212378, 5146851, 8175114, 12915747, 20252564, 31595134, 48964310, 75515995, 115777684, 176696336, 268231986, 405436258

Offset: 0

Author

Vaclav Kotesovec, Oct 08 2018

Keywords

• nonn

Comments

Self-convolution of A006171.

Links

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

Crossrefs

Cf. A006171, A004101, A320235.

Programs

Mathematica

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

Formula

Conjecture: log(a(n)) ~ Pi * sqrt(2*n*log(n)/3).