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) =3a(2) =4a(3) =5a(4) =6a(5) =7a(6) =8a(7) =9a(8) =10a(9) =11a(10) =13a(11) =14a(12) =16a(13) =17a(14) =19a(15) =22a(16) =23a(17) =25a(18) =26a(19) =29a(20) =31a(21) =34a(22) =37a(23) =38a(24) =41a(25) =43a(26) =46a(27) =47a(28) =49a(29) =53