Number of 3-element proper antichains (i.e., antichains such that every two members have nonempty intersection) on an unlabeled n-element set.

A056782

Number of 3-element proper antichains (i.e., antichains such that every two members have nonempty intersection) on an unlabeled n-element set.

Terms

    a(0) =0a(1) =0a(2) =0a(3) =1a(4) =5a(5) =18a(6) =53a(7) =135a(8) =305a(9) =633a(10) =1220a(11) =2217a(12) =3834a(13) =6359a(14) =10172a(15) =15776a(16) =23807a(17) =35075a(18) =50585a(19) =71576a(20) =99551a(21) =136332a(22) =184084a(23) =245384a(24) =323260a(25) =421256a(26) =543484a(27) =694709a(28) =880393a(29) =1106798

External references