Number of collections F of subsets of {1,2,...,n} whose union is itself an element of F.

A246418

Number of collections F of subsets of {1,2,...,n} whose union is itself an element of F.

Terms

    a(0) =1a(1) =3a(2) =13a(3) =159a(4) =33337a(5) =2147648859

External references