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A138212 G.f.: A(x) = 1 + x*(1 + x*(1 + x*(...(1 + x*(...)^(2n))...)^6)^4)^2.

%I A138212 #4 Oct 02 2020 15:54:04
%S A138212 1,1,2,9,68,732,10250,176654,3613044,85476720,2295275372,68949496421,
%T A138212 2290588299708,83374406924240,3299390271801838,141034101443780374,
%U A138212 6475752407825487220,317866884692663325892,16609896989101220207880
%N A138212 G.f.: A(x) = 1 + x*(1 + x*(1 + x*(...(1 + x*(...)^(2n))...)^6)^4)^2.
%H A138212 Vaclav Kotesovec, <a href="/A138212/b138212.txt">Table of n, a(n) for n = 0..340</a>
%e A138212 G.f.: A(x)=1+x*B(x)^2, B(x)=1+x*C(x)^4, C(x)=1+x*D(x)^6, D(x)=1+x*E(x)^8, ...
%e A138212 where A(x),B(x),C(x),... are the g.f. of the sequences given below.
%e A138212 A=[1,1,2,9,68,732,10250,176654,3613044,85476720,...];
%e A138212 B=[1,1,4,30,328,4677,81888,1696086,40520620,1096342026,...];
%e A138212 C=[1,1,6,63,908,16311,347466,8519957,235763712,7259384208,...];
%e A138212 D=[1,1,8,108,1936,42110,1062416,30283824,958845640,...];
%e A138212 E=[1,1,10,165,3540,90550,2646522,86251140,3086189660,...];
%e A138212 F=[1,1,12,234,5848,172107,5725392,210342902,8410505748,...]; ...
%o A138212 (PARI) {a(n)=local(A=1+x+x*O(x^n)); for(j=0, n-1, A=1+x*A^(2*(n-j))); polcoeff(A, n)}
%Y A138212 Cf. A095793, A138211, A138213, A138214, A138215, A138216.
%K A138212 nonn
%O A138212 0,3
%A A138212 _Paul D. Hanna_, Mar 06 2008