Number of set partitions of {1, ..., n} that avoid 3-crossings.

Terms

a(0) =1a(1) =1a(2) =2a(3) =5a(4) =15a(5) =52a(6) =202a(7) =859a(8) =3930a(9) =19095a(10) =97566a(11) =520257a(12) =2877834a(13) =16434105a(14) =96505490a(15) =580864901a(16) =3573876308a(17) =22426075431a(18) =143242527870a(19) =929759705415