Number of partitions of an n-set without blocks of size 6.

Terms

a(0) =1a(1) =1a(2) =2a(3) =5a(4) =15a(5) =52a(6) =202a(7) =870a(8) =4084a(9) =20727a(10) =112825a(11) =654546a(12) =4026487a(13) =26145511a(14) =178550986a(15) =1278168860a(16) =9564026947a(17) =74615547996a(18) =605593775899