Number of partitions of an n-set without blocks of size 5.

Terms

a(0) =1a(1) =1a(2) =2a(3) =5a(4) =15a(5) =51a(6) =197a(7) =835a(8) =3860a(9) =19257a(10) =102997a(11) =586170a(12) =3535645a(13) =22496437a(14) =150454918a(15) =1054235150a(16) =7718958995a(17) =58905868192a(18) =467530598983