Primes having only {2, 7, 8} as digits.

Terms

a(0) =2a(1) =7a(2) =227a(3) =277a(4) =727a(5) =787a(6) =827a(7) =877a(8) =887a(9) =2287a(10) =2777a(11) =2887a(12) =7727a(13) =7877a(14) =8287a(15) =8887a(16) =22277a(17) =22727a(18) =22777a(19) =22787a(20) =22877a(21) =27277a(22) =27827a(23) =28277a(24) =72227a(25) =72277a(26) =72287a(27) =72727a(28) =78277a(29) =78787