A301588 - OEIS

A301588

Expansion of Product_{k>=1} (1 + x^k)^(mod(k,3)).

1, 1, 2, 2, 2, 4, 4, 7, 8, 9, 12, 14, 18, 23, 27, 33, 39, 46, 56, 67, 79, 93, 109, 126, 150, 175, 204, 237, 272, 314, 364, 419, 482, 553, 629, 720, 823, 937, 1069, 1212, 1372, 1555, 1759, 1989, 2247, 2530, 2845, 3200, 3594, 4036, 4528, 5067, 5666, 6333, 7070

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OFFSET

0,3

LINKS

Seiichi Manyama, Table of n, a(n) for n = 0..10000

FORMULA

a(n) ~ exp(Pi*sqrt(n/3)) / (2^(5/3) * 3^(1/4) * n^(3/4)).

MATHEMATICA

nmax = 100; CoefficientList[Series[Product[(1+x^k)^Mod[k, 3], {k, 1, nmax}], {x, 0, nmax}], x]

CROSSREFS

Cf. A010872, A301589.

Sequence in context: A239961 A365541 A308855 * A308921 A308977 A326459

Adjacent sequences: A301585 A301586 A301587 * A301589 A301590 A301591

KEYWORD

nonn

AUTHOR

Vaclav Kotesovec, Mar 24 2018

STATUS

approved