Number of transitive relations on an n-set with exactly three ordered pairs.

Terms

a(0) =0a(1) =0a(2) =2a(3) =43a(4) =276a(5) =1150a(6) =3710a(7) =10017a(8) =23688a(9) =50556a(10) =99450a(11) =183095a(12) =319132a(13) =531258a(14) =850486a(15) =1316525a(16) =1979280a(17) =2900472a(18) =4155378a(19) =5834691a(20) =8046500a(21) =10918390a(22) =14599662a(23) =19263673a(24) =25110296a(25) =32368500a(26) =41299050a(27) =52197327a(28) =65396268a(29) =81269426