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A120575
G.f. satisfies: A(x) = x + 2*x*A(x) + x*A(A(x)).
1
1, 3, 12, 66, 471, 4044, 39711, 433128, 5153655, 66087525, 905350476, 13162855629, 202073897730, 3262403607924, 55206822277551, 976489740673734, 18010559992528317, 345674349652856367, 6891047565127733874
OFFSET
1,2
EXAMPLE
A(x) = x + 3*x^2 + 12*x^3 + 66*x^4 + 471*x^5 + 4044*x^6 + 39711*x^7 +...
A(A(x)) = x + 6*x^2 + 42*x^3 + 339*x^4 + 3102*x^5 + 31623*x^6 +...
PROG
(PARI) {a(n)=local(F=x+x*O(x^n), G=F); for(i=1, n, F=x+2*x*F+x*subst(F, x, F)); polcoeff(F, n)}
CROSSREFS
Cf. A120574.
Sequence in context: A248871 A080599 A349581 * A009362 A123227 A196556
KEYWORD
nonn
AUTHOR
Paul D. Hanna, Jun 15 2006
STATUS
approved