A291583 Expansion of Product_{k>=1} 1/(1 - 2*x^(k^2)).

1, 2, 4, 8, 18, 36, 72, 144, 292, 586, 1172, 2344, 4696, 9396, 18792, 37584, 75186, 150380, 300764, 601528, 1203092, 2406200, 4812408, 9624816, 19249704, 38499446, 76998908, 153997824, 307995792, 615991660, 1231983352, 2463966720, 4927933732, 9855867616

Offset: 0

Author

Vaclav Kotesovec, Aug 31 2017

Keywords

• nonn

Crossrefs

Cf. A001156, A070933.

Programs

Mathematica

nmax = 30; CoefficientList[Series[Product[1/(1 - 2*x^(k^2)), {k, 1, nmax}], {x, 0, nmax}], x]

Formula

a(n) = c * 2^n, where c = Product_{k>=2} 1/(1 - 2^(1-k^2)) = 1.1473740190706250791012378892728990358979800885299281286906257674366893358222...