Number of nonisomorphic graded posets with 0 and non-uniform Hasse graph of rank n, with no 3-element antichain.

A206949

Number of nonisomorphic graded posets with 0 and non-uniform Hasse graph of rank n, with no 3-element antichain.

Terms

    a(0) =0a(1) =0a(2) =0a(3) =3a(4) =24a(5) =135a(6) =657a(7) =2961a(8) =12744a(9) =53244a(10) =218025a(11) =880308a(12) =3518721a(13) =13961727a(14) =55097091a(15) =216546048a(16) =848476296a(17) =3316800555a(18) =12942852624a(19) =50437433079a(20) =196347606849a(21) =763752142233

External references