A166891 Column 1 of triangle A166890.

1, 2, 9, 78, 1038, 18968, 443595, 12681960, 429244197, 16801151910, 746998729887, 37200237947376, 2051666003699226, 124156748403386646, 8180285024067867345, 582970677419310149580, 44684461723038752605932

Offset: 1

Author

Paul D. Hanna, Nov 22 2009

Keywords

• nonn

Comments

Triangle A166890 transforms diagonals in the triangle A166888 of coefficients in the successive iterations of x*(1+x)^2.

Crossrefs

Cf. A166890, A166892, A166893.

Programs

PARI

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