Primes with digital product = 7.

Terms

a(0) =7a(1) =17a(2) =71a(3) =1117a(4) =1171a(5) =11117a(6) =11171a(7) =1111711a(8) =1117111a(9) =1171111a(10) =11111117a(11) =11111171a(12) =71111111a(13) =1117111111a(14) =1711111111a(15) =17111111111