Number of 5-block ordered bicoverings of an unlabeled n-set.

Terms

a(0) =0a(1) =0a(2) =0a(3) =0a(4) =125a(5) =722a(6) =2565a(7) =7180a(8) =17335a(9) =37750a(10) =76093a(11) =144340a(12) =260590a(13) =451440a(14) =755040a(15) =1224964a(16) =1935050a(17) =2985380a(18) =4509590a(19) =6683720a(20) =9736835a(21) =13963670a(22) =19739575a(23) =27538060a(24) =37951265a(25) =51713706a(26) =69729675a(27) =93104700a(28) =123181500