Number of purely crossing partitions of [n].

Terms

a(0) =1a(1) =0a(2) =0a(3) =0a(4) =1a(5) =0a(6) =5a(7) =14a(8) =62a(9) =298a(10) =1494a(11) =8140a(12) =47146a(13) =289250a(14) =1873304a(15) =12756416a(16) =91062073a(17) =679616480a(18) =5290206513a(19) =42858740990a(20) =360686972473