Palindromic primes using only digits 3 and 5.

Terms

a(0) =3a(1) =5a(2) =353a(3) =33533a(4) =35353a(5) =3353533a(6) =3553553a(7) =333535333a(8) =335333533a(9) =355353553a(10) =355555553a(11) =33335353333a(12) =33553335533a(13) =35533333553a(14) =35553535553