Number of topologically connected set partitions of {1,...,n}.

Terms

a(0) =1a(1) =1a(2) =1a(3) =1a(4) =2a(5) =6a(6) =21a(7) =85a(8) =385a(9) =1907a(10) =10205a(11) =58455a(12) =355884a(13) =2290536a(14) =15518391a(15) =110283179a(16) =819675482a(17) =6355429550a(18) =51293023347a(19) =430062712439