A166892 Column 2 of triangle A166890.

1, 4, 30, 364, 6233, 139008, 3833052, 126105168, 4824243516, 210489178476, 10318212622770, 561491367744672, 33588989930164050, 2190978413703916624, 154771816676784778818, 11771103512077651149912, 959000166676677798631894

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+1); 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, 2]}

Crossrefs

Cf. A166890, A166891, A166893.

Sequence in context: A137341 A295899 A291060 * A336712 A185523 A187736

Adjacent sequences: A166889 A166890 A166891 * A166893 A166894 A166895

Keyword

nonn

Author

Paul D. Hanna, Nov 22 2009

Status

approved