a(n) = least positive integer < a(n-1) and not a(i)*a(j)-2 for 1<=i<j<=n.

Terms

a(0) =1a(1) =4a(2) =5a(3) =6a(4) =7a(5) =8a(6) =9a(7) =10a(8) =11a(9) =12a(10) =13a(11) =14a(12) =15a(13) =16a(14) =17a(15) =19a(16) =20a(17) =21a(18) =23a(19) =24a(20) =25a(21) =27a(22) =29a(23) =31a(24) =32a(25) =35a(26) =36a(27) =37a(28) =39a(29) =41