A261630 Expansion of Product_{k>=0} (1+x^(4*k+1))^2.

1, 2, 1, 0, 0, 2, 4, 2, 0, 2, 5, 4, 1, 2, 8, 10, 4, 2, 9, 14, 9, 4, 12, 22, 16, 6, 13, 30, 30, 14, 17, 40, 44, 24, 21, 50, 66, 42, 29, 64, 92, 66, 41, 78, 127, 106, 62, 96, 164, 152, 93, 120, 215, 220, 139, 150, 269, 302, 205, 192, 340, 412, 296, 248, 417

Offset

0,2

Links

Table of n, a(n) for n=0..64.

Formula

a(n) ~ exp(Pi*sqrt(n/6)) / (2 * 6^(1/4) * n^(3/4)).

Mathematica

nmax=80; CoefficientList[Series[Product[(1+x^(4*k+1))^2, {k, 0, nmax}], {x, 0, nmax}], x]

Crossrefs

Cf. A169975, A261634, A261638.

Sequence in context: A247310 A380198 A059220 * A301503 A378103 A378336

Adjacent sequences: A261627 A261628 A261629 * A261631 A261632 A261633

Keyword

nonn

Author

Vaclav Kotesovec, Aug 27 2015

Status

approved