Primes having only {4, 6, 7} as digits.

Terms

a(0) =7a(1) =47a(2) =67a(3) =467a(4) =647a(5) =677a(6) =4447a(7) =7477a(8) =44647a(9) =44777a(10) =46447a(11) =46477a(12) =46747a(13) =47777a(14) =64667a(15) =64747a(16) =66467a(17) =67447a(18) =67477a(19) =67777a(20) =74747a(21) =76667a(22) =76777a(23) =77447a(24) =77477a(25) =77647a(26) =77747a(27) =444677a(28) =444767a(29) =446447