A185619 G.f.: exp( Sum_{n>=1} (x^n/n)*Sum_{k=0..n} C(3n,3k)*x^k ).

1, 1, 2, 12, 41, 134, 535, 2100, 8008, 31483, 125405, 498762, 1995254, 8032580, 32433136, 131333532, 533489683, 2172483451, 8865550544, 36251329866, 148498309280, 609271648415, 2503419660325, 10299986121600, 42429641658643

Offset

0,3

Links

Table of n, a(n) for n=0..24.

Example

 G.f.: A(x) = 1 + x + 2*x^2 + 12*x^3 + 41*x^4 + 134*x^5 +...
log(A(x)) = x*(1+x) + x^2*(1 + 20*x + x^2)/2 + x^3*(1 + 84*x + 84*x^2 + x^3)/3 + x^4*(1 + 220*x + 924*x^2 + 220*x^3 + x^4)/4 +...

Prog

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

Crossrefs

Cf. variant: A051286.

Sequence in context: A127725 A371357 A280174 * A048014 A364598 A094702

Adjacent sequences: A185616 A185617 A185618 * A185620 A185621 A185622

Keyword

nonn

Author

Paul D. Hanna, Mar 19 2011

Status

approved