Members of twin prime pairs using only digits 7 and 9.

Terms

a(0) =79997a(1) =79999a(2) =777977a(3) =777979a(4) =7977797a(5) =7977799a(6) =77997779a(7) =77997977a(8) =77997979a(9) =99777779a(10) =799999799a(11) =977797979a(12) =977999777a(13) =977999779a(14) =979797779a(15) =999799979a(16) =7777997999a(17) =7797799979a(18) =7979997797a(19) =7979997799a(20) =7999777997a(21) =7999777999a(22) =7999797977a(23) =7999797979