a(n) is the number of set-systems using nonempty subsets of {1,...,n} in which all sets have the same size.

A306020

a(n) is the number of set-systems using nonempty subsets of {1,...,n} in which all sets have the same size.

Terms

    a(0) =1a(1) =2a(2) =5a(3) =16a(4) =95a(5) =2110a(6) =1114237a(7) =68723671292

External references