a(n) = n + floor(sqrt(n)).

Terms

a(0) =0a(1) =2a(2) =3a(3) =4a(4) =6a(5) =7a(6) =8a(7) =9a(8) =10a(9) =12a(10) =13a(11) =14a(12) =15a(13) =16a(14) =17a(15) =18a(16) =20a(17) =21a(18) =22a(19) =23a(20) =24a(21) =25a(22) =26a(23) =27a(24) =28a(25) =30a(26) =31a(27) =32a(28) =33a(29) =34