Number of symmetric difference-closed 4-sets consisting of sets consisting of an even number of pairwise disjoint 2-subsets of {1,2,...,n}.

A266503

Number of symmetric difference-closed 4-sets consisting of sets consisting of an even number of pairwise disjoint 2-subsets of {1,2,...,n}.

Terms

    a(0) =0a(1) =0a(2) =0a(3) =0a(4) =0a(5) =15a(6) =105a(7) =735a(8) =4095a(9) =26775a(10) =162855a(11) =1105335a(12) =7187895a(13) =51126075a(14) =356831475a(15) =2676468795a(16) =19890931515a(17) =156769986555

External references