A325950 a(n) = 4^n * [x^n] 1/sqrt(1-x) * Product_{k>=1} (1 + x^k).

1, 6, 30, 204, 1014, 5716, 31212, 163480, 826278, 4320132, 22096324, 110079016, 552324796, 2721379144, 13415146648, 66143801648, 321016593670, 1549027853156, 7506317522132, 35931754574216, 171790455469140, 820584857999448, 3893605676834920, 18400781049682512

Offset

0,2

Links

Table of n, a(n) for n=0..23.

Formula

a(n) ~ exp(Pi*sqrt(n/3)) * 2^(2*n - 3/2) / sqrt(Pi*n).

a(n) = Sum_{j=0..n} A325949(j)*4^(n-j).

Mathematica

nmax = 30; CoefficientList[Series[1/(1-x)^(1/2) * Product[(1+x^k), {k, 1, nmax}], {x, 0, nmax}], x] * 4^Range[0, nmax]

Crossrefs

Cf. A000009, A325947, A325949.

Sequence in context: A005922 A278008 A370751 * A275953 A322170 A362375

Adjacent sequences: A325947 A325948 A325949 * A325951 A325952 A325953

Keyword

nonn

Author

Vaclav Kotesovec, May 28 2019

Status

approved