a(n) = floor(n/2) + floor(n/3).

Terms

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