A171201 G.f. satisfies: A(x) = (1 + x*A(2x))^3.

1, 3, 21, 289, 7566, 380424, 37361616, 7252471584, 2799853666176, 2155959119115264, 3315891500224031232, 10193070293871040606464, 62646640175842537242599936, 769927299959295414569740867584, 18923273743619678311418282019397632, 930154604531789703005691292148132511744

Offset

0,2

Links

Table of n, a(n) for n=0..15.

Formula

Self-convolution cube of A171200 where a(n) = A171200(n+1)/2^n for n>=0.

Mathematica

terms = 16; A[_] = 0; Do[A[x_] = (1 + x*A[2x])^3 + O[x]^terms // Normal, terms]; CoefficientList[A[x], x] (* Stefano Spezia, Apr 02 2025 *)

Prog

(PARI) {a(n)=local(A=1+x+x*O(x^n)); for(i=0, n, A=(1+x*subst(A, x, 2*x))^3); polcoeff(A, n)}

Crossrefs

Cf. A135868, A171200, A171202-A171211.

Sequence in context: A380764 A222035 A361214 * A193206 A055555 A208731

Adjacent sequences: A171198 A171199 A171200 * A171202 A171203 A171204

Keyword

nonn

Author

Paul D. Hanna, Dec 05 2009

Extensions

a(14)-a(15) from Stefano Spezia, Apr 02 2025

Status

approved