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

Terms

a(0) =1a(1) =2a(2) =5a(3) =12a(4) =57a(5) =158a(6) =1101a(7) =5442a(8) =28811a(9) =212502a(10) =2337513a(11) =9422306a(12) =122489967a(13) =1654319046a(14) =13917499277a(15) =111631450818