%I A137646
%S A137646 1,1,4,29,339,5406,109159,2664399,76219485,2499425650,92402751894,
%T A137646 3801481338219,172231146665554,8520038462375370,456913020454609665,
%U A137646 26402792230144908683,1635399597258002744628,108090275300425856404653
%N A137646 a(n) = Sum_{k=0..n} C(k*(k+1)/2, k) * C(k*(k+1)/2, n-k).
%o A137646 (PARI) a(n)=sum(k=0,n,binomial(k*(k+1)/2,k)*binomial(k*(k+1)/2,n-k))
%Y A137646 Sequence in context: A028853 A118795 A099700 this_sequence A000798 A135485 
               A162287
%Y A137646 Adjacent sequences: A137643 A137644 A137645 this_sequence A137647 A137648 
               A137649
%K A137646 nonn
%O A137646 0,3
%A A137646 Paul D. Hanna (pauldhanna(AT)juno.com), Jan 31 2008