A135083 Column 2 of triangle A135080.

1, 3, 15, 112, 1128, 14373, 221952, 4029915, 84135510, 1985740905, 52277994396, 1518768476508, 48261093246396, 1665034362336120, 61979166611850084, 2475861386988907814, 105641851808320785498, 4795101548183135826810

Offset: 0

Author

Paul D. Hanna, Nov 18 2007

Keywords

• nonn

Comments

Triangle A135080 transforms diagonals in the table of coefficients of successive self-compositions of x+x^2 (cf. A122888).

Crossrefs

Cf. A135080 (triangle); other columns: A135081, A135082.

Programs

PARI

{a(n)=local(F=x,M,N,P); M=matrix(n+4,n+4,r,c,F=x;for(i=1,r+c-2,F=subst(F,x,x+x^2+x*O(x^(n+4))));polcoeff(F,c)); N=matrix(n+3,n+3,r,c,M[r,c]);P=matrix(n+3,n+3,r,c,M[r+1,c]);(P~*N~^-1)[n+3,3]}