A166887 Column 3 of triangle A166884.

1, 3, 18, 157, 1812, 25989, 445255, 8865333, 201058614, 5114874693, 144207579708, 4462151144553, 150316762118466, 5475746846833734, 214463847533104125, 8986421286160678944, 401112805593137715609, 18999650382886046745879

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, A166886.

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+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+3, 3]}