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%I #2 Mar 30 2012 18:37:18
%S 1,1,3,15,114,1159,14838,229401,4159662,86580636,2034850425,
%T 53303009286,1539990513588,48648616439496,1668228105283302,
%U 61715049142446537,2450018515737072792,103892256368706869356,4686744256645813560957
%N Column 1 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); 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]}
%Y Cf. A166880, A166884, A166886, A166887.
%K nonn
%O 1,3
%A _Paul D. Hanna_, Nov 21 2009
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