A166886 Column 2 of triangle A166884.

1, 2, 9, 62, 593, 7266, 108720, 1922166, 39212154, 906623004, 23429034168, 669203550906, 20935080981744, 711872134399868, 26142553369667634, 1031146768716808794, 43475757877044427198, 1951261759908828697902

Offset: 1

Author

Paul D. Hanna, Nov 21 2009

Keywords

• nonn

Comments

Triangle A166884 transforms diagonals in the triangle A166880 of coefficients in the successive iterations of x+x^2+x^3.

Crossrefs

Cf. A166880, A166884, A166885, A166887.

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+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, 2]}