Number of 6-block ordered tricoverings of an unlabeled n-set.

Terms

a(0) =0a(1) =0a(2) =120a(3) =3030a(4) =24552a(5) =130740a(6) =551640a(7) =1997415a(8) =6470420a(9) =19219462a(10) =53187840a(11) =138658760a(12) =343297780a(13) =812249250a(14) =1845669776a(15) =4044119530a(16) =8573706300a(17) =17637474350a(18) =35294157340a(19) =68850086745a(20) =131179071560a(21) =244518601660a(22) =446576824800a(23) =800201972990