a(n) = Sum_{k=1..n} floor(n/k^2).

Terms

a(0) =1a(1) =2a(2) =3a(3) =5a(4) =6a(5) =7a(6) =8a(7) =10a(8) =12a(9) =13a(10) =14a(11) =16a(12) =17a(13) =18a(14) =19a(15) =22a(16) =23a(17) =25a(18) =26a(19) =28a(20) =29a(21) =30a(22) =31a(23) =33a(24) =35a(25) =36a(26) =38a(27) =40a(28) =41a(29) =42