Number of 4-element ordered antichains on an unlabeled n-element set; T_1-hypergraphs with 4 labeled nodes and n hyperedges.

A056069

Number of 4-element ordered antichains on an unlabeled n-element set; T_1-hypergraphs with 4 labeled nodes and n hyperedges.

Terms

    a(0) =25a(1) =454a(2) =3818a(3) =21420a(4) =92805a(5) =335152a(6) =1055944a(7) =2990020a(8) =7767357a(9) =18789070a(10) =42797602a(11) =92588216a(12) =191542842a(13) =381000192a(14) =731941256a(15) =1363109096a(16) =2468549141a(17) =4358716470a(18) =7520830306a(19) =12706161124a(20) =21054530855a(21) =34269633840a(22) =54863015040a(23) =86489873580a(24) =134406530985

External references