Isotopy classes of unordered Latin bi-trades of size n.

Terms

a(0) =0a(1) =0a(2) =0a(3) =1a(4) =0a(5) =3a(6) =1a(7) =13a(8) =7a(9) =59a(10) =70a(11) =553a(12) =1277a(13) =7661a(14) =32395a(15) =199205a(16) =1149306a(17) =7752187a(18) =53913897