A138213 - OEIS

%I #2 Mar 30 2012 18:37:09

%S 1,1,3,21,244,4002,84909,2209947,68121822,2425846806,97969327890,

%T 4423628854404,220806455598561,12072207455321168,717431790926502954,

%U 46045783798588216767,3174068594948910976851,233875508656473241657578

%N G.f.: A(x) = 1 + x*(1 + x*(1 + x*(...(1 + x*(...)^(3n))...)^9)^6)^3.

%e 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,...

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

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

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

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

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

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

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

%o (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)}

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

%K nonn

%O 0,3

%A _Paul D. Hanna_, Mar 06 2008