Numbers congruent to {0, 1, 2} mod 4: a(n) = floor(4*n/3).

Terms

a(0) =0a(1) =1a(2) =2a(3) =4a(4) =5a(5) =6a(6) =8a(7) =9a(8) =10a(9) =12a(10) =13a(11) =14a(12) =16a(13) =17a(14) =18a(15) =20a(16) =21a(17) =22a(18) =24a(19) =25a(20) =26a(21) =28a(22) =29a(23) =30a(24) =32a(25) =33a(26) =34a(27) =36a(28) =37a(29) =38