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

Terms

a(0) =1a(1) =4a(2) =6a(3) =7a(4) =10a(5) =11a(6) =15a(7) =16a(8) =18a(9) =19a(10) =23a(11) =24a(12) =26a(13) =27a(14) =29a(15) =30a(16) =34a(17) =35a(18) =39a(19) =40a(20) =42a(21) =43a(22) =45a(23) =46a(24) =50a(25) =51a(26) =55a(27) =56a(28) =60a(29) =61