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

Terms

a(0) =1a(1) =2a(2) =4a(3) =5a(4) =6a(5) =7a(6) =9a(7) =11a(8) =13a(9) =15a(10) =16a(11) =17a(12) =19a(13) =21a(14) =23a(15) =25a(16) =27a(17) =29a(18) =31a(19) =33a(20) =37a(21) =39a(22) =41a(23) =43a(24) =47a(25) =49a(26) =51a(27) =53a(28) =57a(29) =59