a(n) = (1/4)*s(n), where s(n) is the n-th multiple of 4 in A026166.

Terms

a(0) =1a(1) =2a(2) =4a(3) =5a(4) =7a(5) =3a(6) =10a(7) =11a(8) =13a(9) =14a(10) =16a(11) =6a(12) =19a(13) =20a(14) =22a(15) =8a(16) =25a(17) =9a(18) =28a(19) =29a(20) =31a(21) =32a(22) =34a(23) =12a(24) =37a(25) =38a(26) =40a(27) =41a(28) =43a(29) =15