A266943 Expansion of Product_{k>=1} 1 / (1 - 2*x^k)^2.

1, 4, 16, 52, 160, 452, 1232, 3204, 8112, 19956, 48112, 113732, 264816, 607876, 1379264, 3096372, 6888784, 15201156, 33306752, 72510916, 156972960, 338089844, 724883552, 1547816708, 3292816416, 6981664708, 14758159472, 31110217524, 65415167744, 137230388228

Offset: 0

Author

Vaclav Kotesovec, Jan 06 2016

Keywords

• nonn

Links

• Vaclav Kotesovec, Table of n, a(n) for n = 0..1000

Crossrefs

Cf. A048651, A070933, A266944, A266945.

Programs

Mathematica

nmax = 40; CoefficientList[Series[Product[1/(1-2*x^k)^2, {k, 1, nmax}], {x, 0, nmax}], x]

Formula

a(n) ~ c * n * 2^n, where c = 1/A048651^2 = 11.9906141505474711257730652493... .