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A166902 Column 2 of triangle A166900. 4
1, 9, 84, 935, 12480, 196623, 3591560, 74847168, 1755406674, 45804773872, 1317004696656, 41386864224420, 1411592788770580, 51942256939923051, 2051313029747633376, 86548588478842559964, 3885584044838123386104 (list; graph; refs; listen; history; text; internal format)
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 * A275394 A236385 A335670

Adjacent sequences:  A166899 A166900 A166901 * A166903 A166904 A166905

KEYWORD

nonn

AUTHOR

Paul D. Hanna, Nov 27 2009

STATUS

approved

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Last modified June 14 21:27 EDT 2021. Contains 345041 sequences. (Running on oeis4.)