login
A120916
G.f. satisfies: A(x) = C(2x)*A(x^3*C(2x)^4), where C(x) is the g.f. of the Catalan numbers (A000108).
3
1, 2, 8, 42, 244, 1504, 9656, 63856, 431872, 2972778, 20756036, 146627648, 1046060836, 7525452296, 54530660832, 397628393728, 2915496099136, 21481907631872, 158975372309176, 1181109256858096, 8806197969093184
OFFSET
0,2
COMMENTS
Self-convolution equals A120915, which equals column 0 of triangle A120914 (cascadence of (1+2x)^2).
PROG
(PARI) {a(n)=local(A=1+2*x, C=(1/x*serreverse(x/(1+4*x+4*x^2+x*O(x^n))))^(1/2)); for(i=0, n, A=C*subst(A, x, x^3*C^4 +x*O(x^n))); polcoeff(A, n, x)}
CROSSREFS
KEYWORD
nonn
AUTHOR
Paul D. Hanna, Jul 17 2006
STATUS
approved