0,3

G.f.: A(x)=1+x*B(x)^3, B(x)=1+x*C(x)^6, C(x)=1+x*D(x)^9, D(x)=1+x*E(x)^12,...

where A(x),B(x),C(x),... are the g.f. of the sequences given below.

A=[1,1,3,21,244,4002,84909,2209947,68121822,2425846806,...];

B=[1,1,6,69,1154,25062,665862,20869399,752900220,30714860088,...];

C=[1,1,9,144,3162,86346,2789703,103536696,4329341244,...];

D=[1,1,12,246,6700,221145,8453892,364604520,17444393868,...];

E=[1,1,15,375,12200,472875,20921433,1031067730,55735025670,...];

F=[1,1,18,531,20094,895077,45035802,2500543500,150992211456,...]; ...

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

Cf. A095793, A138211, A138212, A138214, A138215, A138216.

Sequence in context: A138903 A058562 A145083 this_sequence A012131 A098278 A066206

Adjacent sequences: A138210 A138211 A138212 this_sequence A138214 A138215 A138216

nonn

Paul D. Hanna (pauldhanna(AT)juno.com), Mar 06 2008