OFFSET
0,3
EXAMPLE
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,...]; ...
PROG
(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)}
CROSSREFS
KEYWORD
nonn
AUTHOR
Paul D. Hanna, Mar 06 2008
STATUS
approved