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

1,2

Comments

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

Links

Table of n, a(n) for n=1..18.

Prog

(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]}

Crossrefs

Cf. A166880, A166884, A166885, A166886.

Sequence in context: A246529 A305824 A116956 * A075678 A341331 A089901

Adjacent sequences: A166884 A166885 A166886 * A166888 A166889 A166890

Keyword

nonn

Author

Paul D. Hanna, Nov 21 2009

Status

approved