Number of bipartite partitions of (n,n) into distinct pairs.

Terms

a(0) =1a(1) =2a(2) =5a(3) =17a(4) =46a(5) =123a(6) =323a(7) =809a(8) =1966a(9) =4660a(10) =10792a(11) =24447a(12) =54344a(13) =118681a(14) =254991a(15) =539852a(16) =1127279a(17) =2323849a(18) =4733680a(19) =9535079a(20) =19005282a(21) =37507802a(22) =73333494a(23) =142112402a(24) =273092320a(25) =520612305a(26) =984944052a(27) =1849920722a(28) =3450476080a(29) =6393203741