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%I #6 Mar 30 2012 18:37:34
%S 1,3,21,156,1335,12153,116778,1160715,11848530,123420648,1306709841,
%T 14019657771,152092615971,1665531792021,18386262679557,
%U 204393214435791,2286101345820933,25708109998131381,290490321604346535,3296566844230833750,37555644504960139647
%N G.f. satisfies: A(x) = 1/Product_{n>=1} (1 - 3*x^n*A(x^n)).
%e G.f.: A(x) = 1 + 3*x + 21*x^2 + 156*x^3 + 1335*x^4 + 12153*x^5 +...
%e where
%e A(x) = 1/((1 - 3*x*A(x)) * (1 - 3*x^2*A(x^2)) * (1 - 3*x^3*A(x^3)) *...).
%o (PARI) {a(n)=local(A=1+x); for(i=1, n, A=1/prod(k=1, n, (1-3*x^k*subst(A, x, x^k+x*O(x^n))))); polcoeff(A, n)}
%Y Cf. A050383, A196192, A205772.
%K nonn
%O 0,2
%A _Paul D. Hanna_, Jan 31 2012
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