a(n) = Sum_{k=1..n} k^floor((n-k)/k).

Terms

a(0) =1a(1) =2a(2) =3a(3) =5a(4) =6a(5) =11a(6) =12a(7) =20a(8) =27a(9) =40a(10) =41a(11) =93a(12) =94a(13) =133a(14) =208a(15) =328a(16) =329a(17) =658a(18) =659a(19) =1217a(20) =1746a(21) =2269a(22) =2270a(23) =5768a(24) =6269a(25) =8330a(26) =12777a(27) =20253a(28) =20254a(29) =45253