A166893 Column 3 of triangle A166890.

1, 6, 63, 986, 20685, 545736, 17365336, 647216568, 27653205177, 1332422277828, 71470510481961, 4223498675806638, 272615162534575302, 19082609490868539738, 1439738711122827542742, 116468234559061615308870

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, A166892.

Programs

PARI

{a(n)=local(F=x, M, N, P, m=n+2); 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+2, 3]}