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

Terms

a(0) =0a(1) =1a(2) =3a(3) =5a(4) =10a(5) =13a(6) =30a(7) =39a(8) =84a(9) =143a(10) =290a(11) =424a(12) =1120a(13) =1697a(14) =3521a(15) =6633a(16) =14012a(17) =22721a(18) =53529a(19) =88607a(20) =189749a(21) =356024a(22) =730697a(23) =1256272a(24) =2889484a(25) =5006918a(26) =10399649a(27) =19706342a(28) =40954970a(29) =72663140