Primes having only {1, 4, 7} as digits.

Terms

a(0) =7a(1) =11a(2) =17a(3) =41a(4) =47a(5) =71a(6) =1117a(7) =1171a(8) =1447a(9) =1471a(10) =1741a(11) =1747a(12) =1777a(13) =4111a(14) =4177a(15) =4441a(16) =4447a(17) =7177a(18) =7411a(19) =7417a(20) =7477a(21) =7717a(22) =7741a(23) =11117a(24) =11171a(25) =11177a(26) =11411a(27) =11447a(28) =11471a(29) =11717