%I A123611
%S A123611 1,2,4,8,20,52,160,492,1620,5408,18504,64132,225440,800048,2865720,
%T A123611 10341208,37568340,137270956,504176992,1860277044,6892335720,
%U A123611 25631327688,95640894056,357975249028,1343650267296,5056424257552
%N A123611 Row sums of triangle A123610.
%F A123611 a(n) = 2*A047996(2*n,n) = 2*A003239(n) for n>0, where A047996 is the 
               triangle of circular binomial coefficients and A003239(n) = number 
               of rooted planar trees with n non-root nodes.
%o A123611 (PARI) {a(n)=sum(k=0,n,if(k==0,1,(1/n)*sumdiv(n,d,if(gcd(k,d)==d, eulerphi(d)*binomial(n/
               d,k/d)^2,0))))}
%Y A123611 Cf. A047996, A003239; A123610 (triangle), A123612 (antidiagonal sums); 
               central terms: A123617, A123618.
%Y A123611 Sequence in context: A078160 A089976 A000980 this_sequence A082279 A113180 
               A000116
%Y A123611 Adjacent sequences: A123608 A123609 A123610 this_sequence A123612 A123613 
               A123614
%K A123611 nonn
%O A123611 0,2
%A A123611 Paul D. Hanna (pauldhanna(AT)juno.com), Oct 03 2006