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

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, A166891, A166893.

Programs

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]}