login
Column 2 of triangle A166884.
3

%I #2 Mar 30 2012 18:37:18

%S 1,2,9,62,593,7266,108720,1922166,39212154,906623004,23429034168,

%T 669203550906,20935080981744,711872134399868,26142553369667634,

%U 1031146768716808794,43475757877044427198,1951261759908828697902

%N Column 2 of triangle A166884.

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

%o (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]}

%Y Cf. A166880, A166884, A166885, A166887.

%K nonn

%O 1,2

%A _Paul D. Hanna_, Nov 21 2009