Primes having only {6, 7, 9} as digits.

Terms

a(0) =7a(1) =67a(2) =79a(3) =97a(4) =677a(5) =769a(6) =797a(7) =967a(8) =977a(9) =997a(10) =6679a(11) =6779a(12) =6967a(13) =6977a(14) =6997a(15) =7669a(16) =7699a(17) =9677a(18) =9679a(19) =9697a(20) =9767a(21) =9769a(22) =9967a(23) =66697a(24) =66797a(25) =66977a(26) =67679a(27) =67699a(28) =67777a(29) =67967