a(n) = c([ 2n/3 ]) + n, with a(1) = 1, a(2) = 4, c = complement to a.

Terms

a(0) =1a(1) =4a(2) =6a(3) =7a(4) =10a(5) =14a(6) =15a(7) =17a(8) =20a(9) =21a(10) =23a(11) =25a(12) =26a(13) =30a(14) =33a(15) =34a(16) =36a(17) =40a(18) =41a(19) =44a(20) =48a(21) =49a(22) =51a(23) =53a(24) =54a(25) =57a(26) =59a(27) =60a(28) =64a(29) =67