Species of unordered Latin bi-trades of size n.

Terms

a(0) =0a(1) =0a(2) =0a(3) =1a(4) =0a(5) =1a(6) =1a(7) =5a(8) =3a(9) =17a(10) =19a(11) =131a(12) =262a(13) =1448a(14) =5743a(15) =34514a(16) =194239a(17) =1302209a(18) =9011123