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%I #2 Mar 30 2012 18:37:18
%S 1,4,30,364,6233,139008,3833052,126105168,4824243516,210489178476,
%T 10318212622770,561491367744672,33588989930164050,2190978413703916624,
%U 154771816676784778818,11771103512077651149912,959000166676677798631894
%N Column 2 of triangle A166890.
%C Triangle A166890 transforms diagonals in the triangle A166888 of coefficients in the successive iterations of x*(1+x)^2.
%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+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+1, 2]}
%Y Cf. A166890, A166891, A166893.
%K nonn
%O 1,2
%A _Paul D. Hanna_, Nov 22 2009
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