a(n) = Sum_{k=1..n} Stirling2(n,k) * floor(n/k).

Terms

a(0) =1a(1) =3a(2) =7a(3) =25a(4) =71a(5) =360a(6) =1310a(7) =7195a(8) =35740a(9) =213318a(10) =1132154a(11) =8409475a(12) =50344672a(13) =366939569a(14) =2728237607a(15) =21375289293a(16) =159969524749