Number of sets of subsets of {1..n} that are closed under union and cover all n vertices.
A326906
Number of sets of subsets of {1..n} that are closed under union and cover all n vertices.
Terms
- a(0) =2a(1) =2a(2) =8a(3) =90a(4) =4542a(5) =2747402a(6) =151930948472
External references
- oeis: A326906