%I A070968
%S A070968 0,1,15,204,3940,113865,4662231,256485040,18226108944,1623855701385,
%T A070968 177195820499335,23237493232953516,3605437233380095620,
%U A070968 653193551573628900289,136634950180317224866335
%N A070968 Number of cycles in the bipartite graph K(n,n).
%F A070968 a(n) = sum k=2..n C(n, k)^2 * k! * (k-1)! / 2.
%t A070968 Table[ Sum[ Binomial[n, k]^2*k!*(k - 1)!, {k, 2, n}]/2, {n, 1, 17}]
%o A070968 (PARI) for(n=1,50,print1(sum(k=2,n,binomial(n,k)^2 * k! * (k-1)!/2),",
               "))
%Y A070968 Cf. A002807, A068087.
%Y A070968 Sequence in context: A048444 A002007 A012566 this_sequence A075280 A093747 
               A061637
%Y A070968 Adjacent sequences: A070965 A070966 A070967 this_sequence A070969 A070970 
               A070971
%K A070968 nonn
%O A070968 1,3
%A A070968 Sharon Sela (sharonsela(AT)hotmail.com), May 17 2002
%E A070968 More terms from Benoit Cloitre (benoit7848c(AT)orange.fr) and Robert 
               G. Wilson v (rgwv(AT)rgwv.com), May 20 2002