Numbers which yield a prime whenever a 3 is prefixed, appended or inserted.

Terms

a(0) =1a(1) =7a(2) =11a(3) =17a(4) =31a(5) =37a(6) =73a(7) =121a(8) =271a(9) =331a(10) =343a(11) =359a(12) =361a(13) =373a(14) =533a(15) =637a(16) =673a(17) =733a(18) =793a(19) =889a(20) =943a(21) =1033a(22) =1183a(23) =2297a(24) =3013a(25) =3119a(26) =3223a(27) =3353a(28) =3403a(29) =3461