a(n) = Sum_{k=0..floor(n/5)} |Stirling1(n - 4*k,k)|.

Terms

a(0) =1a(1) =0a(2) =0a(3) =0a(4) =0a(5) =1a(6) =1a(7) =2a(8) =6a(9) =24a(10) =121a(11) =723a(12) =5051a(13) =40370a(14) =363154a(15) =3630565a(16) =39929874a(17) =479111219a(18) =6228047601a(19) =87188921464