a(n) is the number of unordered pairs of disjoint set partitions of an n-element set.
A152525
a(n) is the number of unordered pairs of disjoint set partitions of an n-element set.
Terms
- a(0) =0a(1) =0a(2) =1a(3) =7a(4) =65a(5) =811a(6) =12762a(7) =244588a(8) =5574956a(9) =148332645a(10) =4538695461a(11) =157768581675
External references
- oeis: A152525