Primes having only {2, 4, 6, 7} as digits.

Terms

a(0) =2a(1) =7a(2) =47a(3) =67a(4) =227a(5) =277a(6) =467a(7) =647a(8) =677a(9) =727a(10) =2267a(11) =2447a(12) =2467a(13) =2477a(14) =2647a(15) =2677a(16) =2767a(17) =2777a(18) =4447a(19) =6247a(20) =6277a(21) =6427a(22) =7247a(23) =7477a(24) =7727a(25) =22247a(26) =22277a(27) =22447a(28) =22727a(29) =22777