A166901 Column 1 of triangle A166900.

1, 4, 21, 156, 1540, 19160, 288813, 5123608, 104657520, 2420186616, 62514944778, 1784255891484, 55767065855228, 1894463658611680, 69504774168222109, 2738952451360200312, 115380142451625516088, 5174227834995200591840

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..17.

Prog

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

Crossrefs

Cf. A166900, A166902, A166903, A122888, A135080.

Sequence in context: A335848 A316370 A357424 * A060072 A157503 A144010

Adjacent sequences: A166898 A166899 A166900 * A166902 A166903 A166904

Keyword

nonn

Author

Paul D. Hanna, Nov 27 2009

Status

approved