Primes where every other digit is 7 starting with the rightmost digit, and no other digit is 7.

Terms

a(0) =7a(1) =17a(2) =37a(3) =47a(4) =67a(5) =97a(6) =727a(7) =757a(8) =787a(9) =797a(10) =1747a(11) =1787a(12) =2707a(13) =2767a(14) =2797a(15) =3727a(16) =3767a(17) =3797a(18) =4787a(19) =5717a(20) =5737a(21) =6737a(22) =8707a(23) =8737a(24) =8747a(25) =9767a(26) =9787a(27) =70717a(28) =71707a(29) =72707