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

Terms

a(0) =2a(1) =7a(2) =67a(3) =227a(4) =277a(5) =677a(6) =727a(7) =2267a(8) =2677a(9) =2767a(10) =2777a(11) =6277a(12) =7727a(13) =22277a(14) =22727a(15) =22777a(16) =26227a(17) =26267a(18) =26627a(19) =26777a(20) =27277a(21) =27767a(22) =62627a(23) =67777a(24) =72227a(25) =72277a(26) =72727a(27) =72767a(28) =76667a(29) =76777