%I #4 Mar 30 2012 18:37:01
%S 1,1,3,8,26,91,349,1431,6253,28860,140064,711433,3768601,20754377,
%T 118513699,700096184,4269686754,26835429731,173541095213,
%U 1153074832175,7861658903709,54937031541660,393050395468752,2876341596372209
%N O.g.f.: A(x) = Sum_{n>=0} x^n*Product_{k=0..n} (1 + k*x)^2.
%e A(x) = 1 + x*(1+x)^2 + x^2*(1+x)^2*(1+2x)^2 + x^3*(1+x)^2*(1+2x)^2*(1+3x)^2 +...
%o (PARI) a(n)=polcoeff(sum(k=0,n,x^k*prod(j=0,k,1+j*x+x*O(x^n))^2),n)
%K nonn
%O 0,3
%A _Paul D. Hanna_, Oct 28 2006
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