A166902 Column 2 of triangle A166900.

1, 9, 84, 935, 12480, 196623, 3591560, 74847168, 1755406674, 45804773872, 1317004696656, 41386864224420, 1411592788770580, 51942256939923051, 2051313029747633376, 86548588478842559964, 3885584044838123386104

Offset: 0

Author

Paul D. Hanna, Nov 27 2009

Keywords

• nonn

Comments

Triangle A166900 transforms rows into diagonals in the table of coefficients of successive iterations of x+x^2 (cf. A122888).

Crossrefs

Cf. A166900, A166901, A166903, A122888, A135080.

Programs

PARI

{a(n)=local(F=x, M, N, P); M=matrix(n+4, n+4, r, c, F=x;for(i=1, r+c-2, F=subst(F, x, x+x^2+x*O(x^(n+4)))); polcoeff(F, c)); N=matrix(n+3, n+3, r, c, F=x;for(i=1, r, F=subst(F, x, x+x^2+x*O(x^(n+4)))); polcoeff(F, c)); P=matrix(n+3, n+3, r, c, M[r+1, c]); (P~*N~^-1)[n+3, 3]}