a(n) = Sum_{k=1..n} k! * floor(n/k).

Terms

a(0) =1a(1) =4a(2) =11a(3) =38a(4) =159a(5) =888a(6) =5929a(7) =46276a(8) =409163a(9) =4038086a(10) =43954887a(11) =522957240a(12) =6749978041a(13) =93928274284