Primes that contain digits 5 and 7 only.

Terms

a(0) =5a(1) =7a(2) =557a(3) =577a(4) =757a(5) =5557a(6) =7577a(7) =7757a(8) =57557a(9) =75557a(10) =75577a(11) =77557a(12) =555557a(13) =575557a(14) =575777a(15) =577757a(16) =757577a(17) =775757a(18) =775777a(19) =5555777a(20) =5557757a(21) =5575777a(22) =5577577a(23) =5755577a(24) =5775557a(25) =5777557a(26) =7575577a(27) =7577777a(28) =55555777a(29) =55575757