Number of pairs of set partitions of {1,2,...,n} whose meet is {{1},{2},...,{n}} and join is {{1,2,...,n}}.
A181939
Number of pairs of set partitions of {1,2,...,n} whose meet is {{1},{2},...,{n}} and join is {{1,2,...,n}}.
Terms
- a(0) =1a(1) =1a(2) =2a(3) =8a(4) =56a(5) =552a(6) =7202a(7) =118456a(8) =2369922a(9) =56230544a(10) =1552048082a(11) =49080888144
External references
- oeis: A181939