%I #21 Dec 08 2020 21:59:46
%S 2,16,144,9216,57600,14515200,203212800,65028096000,1580182732800,
%T 421382062080000,6373403688960000,38546345510830080000,
%U 310206304349061120000,212801524783455928320000,47880343076277583872000000
%N Number of graceful labelings of the complete bipartite graph K_{n,n}.
%C For n > 1, a(n) is a nonzero multiple of 4*(n!)^2. - _Bert Dobbelaere_, Sep 30 2020
%H Eric Weisstein's World of Mathematics, <a href="http://mathworld.wolfram.com/CompleteBipartiteGraph.html">Complete Bipartite Graph</a>
%H Eric Weisstein's World of Mathematics, <a href="http://mathworld.wolfram.com/GracefulLabeling.html">Graceful Labeling</a>
%F a(n) = 4*(n!)^2 A335619(n) for n > 1.
%Y Cf. A335619 (number of fundamentally different graceful labelings).
%K nonn,more
%O 1,1
%A _Eric W. Weisstein_, Sep 22 2020
%E a(5)-a(9) from _Bert Dobbelaere_, Sep 30 2020
%E a(10)-a(15) (using terms in A335619) from _Alois P. Heinz_, Dec 08 2020