Primes having only {3, 4, 7} as digits.

Terms

a(0) =3a(1) =7a(2) =37a(3) =43a(4) =47a(5) =73a(6) =337a(7) =347a(8) =373a(9) =433a(10) =443a(11) =733a(12) =743a(13) =773a(14) =3343a(15) =3347a(16) =3373a(17) =3433a(18) =3733a(19) =4337a(20) =4373a(21) =4447a(22) =4733a(23) =7333a(24) =7433a(25) =7477a(26) =33343a(27) =33347a(28) =33377a(29) =33773