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A166893
Column 3 of triangle A166890.
3
1, 6, 63, 986, 20685, 545736, 17365336, 647216568, 27653205177, 1332422277828, 71470510481961, 4223498675806638, 272615162534575302, 19082609490868539738, 1439738711122827542742, 116468234559061615308870
OFFSET
1,2
COMMENTS
Triangle A166890 transforms diagonals in the triangle A166888 of coefficients in the successive iterations of x*(1+x)^2.
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+2*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, 3]}
CROSSREFS
KEYWORD
nonn
AUTHOR
Paul D. Hanna, Nov 22 2009
STATUS
approved