A166891 Column 1 of triangle A166890.

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

Offset

1,2

Comments

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

Links

Table of n, a(n) for n=1..17.

Prog

(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]}

Crossrefs

Cf. A166890, A166892, A166893.

Sequence in context: A006041 A192551 A121131 * A184894 A111196 A229211

Adjacent sequences: A166888 A166889 A166890 * A166892 A166893 A166894

Keyword

nonn

Author

Paul D. Hanna, Nov 22 2009

Status

approved