A202942 G.f.: [ Sum_{n>=0} (n+1)*(n+2)/2 * 2^(n^2) * x^n ]^(1/3).

1, 2, 28, 1592, 320416, 233502272, 640425828736, 6752822665196288, 276674110514780283136, 44326172948662599528407552, 27888135883706078415361423227904, 69119744225611603596101581358820128768, 676455661208111898411893322163207326229331968

Offset

0,2

Links

Table of n, a(n) for n=0..12.

Formula

a(2*n) == 1 (mod 3); a(2*n+1) == 2 (mod 3).

Example

G.f.: A(x) = 1 + 2*x + 28*x^2 + 1592*x^3 + 320416*x^4 + 233502272*x^5 +...
where
A(x)^3 = 1 + 3*2*x + 6*2^4*x^2 + 10*2^9*x^3 + 15*2^16*x^4 + 21*2^25*x^5 +...

Prog

(PARI) {a(n)=polcoeff(sum(m=0, n, (m+1)*(m+2)/2*2^(m^2)*x^m+x*O(x^n))^(1/3), n)}

Crossrefs

Sequence in context: A361405 A331839 A238817 * A356518 A355070 A326366

Adjacent sequences: A202939 A202940 A202941 * A202943 A202944 A202945

Keyword

nonn

Author

Paul D. Hanna, Dec 26 2011

Status

approved