The nonprime numbers: 1 together with the composite numbers, A002808.

Terms

a(0) =1a(1) =4a(2) =6a(3) =8a(4) =9a(5) =10a(6) =12a(7) =14a(8) =15a(9) =16a(10) =18a(11) =20a(12) =21a(13) =22a(14) =24a(15) =25a(16) =26a(17) =27a(18) =28a(19) =30a(20) =32a(21) =33a(22) =34a(23) =35a(24) =36a(25) =38a(26) =39a(27) =40a(28) =42a(29) =44