A120575 G.f. satisfies: A(x) = x + 2*x*A(x) + x*A(A(x)).

1, 3, 12, 66, 471, 4044, 39711, 433128, 5153655, 66087525, 905350476, 13162855629, 202073897730, 3262403607924, 55206822277551, 976489740673734, 18010559992528317, 345674349652856367, 6891047565127733874

Offset

1,2

Links

Table of n, a(n) for n=1..19.

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

Adjacent sequences: A120572 A120573 A120574 * A120576 A120577 A120578

Keyword

nonn

Author

Paul D. Hanna, Jun 15 2006

Status

approved