A128329 Main diagonal of table A128325.

1, 1, 4, 30, 321, 4389, 72512, 1399755, 30865353, 764755508, 21024535960, 634924059276, 20890221475598, 743727414390456, 28484480606420928, 1167761832049224515, 51022550712426870397, 2366859765773183488674

Offset

0,3

Links

Table of n, a(n) for n=0..17.

Formula

a(n) = [x^n] {1 + H(x)}, where H(x) is the (n+2)-th self-composition of G(x) and G(x) = x + x*G(G(x)) is the g.f. of A030266.

Prog

(PARI) {a(n)=local(A=1+x, B); for(i=0, n, A=1+x*A*subst(A, x, x*A+x*O(x^n))); B=A; for(i=1, n, B=subst(B, x, x*A+x*O(x^n))); polcoeff(B, n)}

Crossrefs

Cf. A030266; A128325 (table), A128326 (row 1), A128327 (row 2), A128328 (row 3).

Sequence in context: A293191 A367963 A180623 * A211828 A277759 A006149

Adjacent sequences: A128326 A128327 A128328 * A128330 A128331 A128332

Keyword

nonn

Author

Paul D. Hanna, Mar 11 2007

Status

approved