A166902 Column 2 of triangle A166900.

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

Offset

0,2

Comments

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

Links

Table of n, a(n) for n=0..16.

Prog

(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]}

Crossrefs

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

Sequence in context: A152056 A086627 A024118 * A348316 A275394 A236385

Adjacent sequences: A166899 A166900 A166901 * A166903 A166904 A166905

Keyword

nonn

Author

Paul D. Hanna, Nov 27 2009

Status

approved