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

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, A166902, A166903, A122888, A135080.

Programs

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]}