A166885 Column 1 of triangle A166884.

1, 1, 3, 15, 114, 1159, 14838, 229401, 4159662, 86580636, 2034850425, 53303009286, 1539990513588, 48648616439496, 1668228105283302, 61715049142446537, 2450018515737072792, 103892256368706869356, 4686744256645813560957

Offset

1,3

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..19.

Prog

(PARI) {a(n)=local(F=x, M, N, P, m=n); 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+1, 1]}

Crossrefs

Cf. A166880, A166884, A166886, A166887.

Sequence in context: A123853 A357794 A335531 * A346224 A082163 A375449

Adjacent sequences: A166882 A166883 A166884 * A166886 A166887 A166888

Keyword

nonn

Author

Paul D. Hanna, Nov 21 2009

Status

approved