Numbers x such that 1 + 3*x*(x-1) is a ("cuban") prime (cf. A002407).

Terms

a(0) =2a(1) =3a(2) =4a(3) =5a(4) =7a(5) =10a(6) =11a(7) =12a(8) =14a(9) =15a(10) =18a(11) =24a(12) =25a(13) =26a(14) =28a(15) =29a(16) =31a(17) =33a(18) =35a(19) =38a(20) =39a(21) =42a(22) =43a(23) =46a(24) =49a(25) =50a(26) =53a(27) =56a(28) =59a(29) =63