Primes consisting only of digits 1 and 3 occurring with equal frequency.

Terms

a(0) =13a(1) =31a(2) =11313331a(3) =11333131a(4) =13111333a(5) =13131133a(6) =13131331a(7) =13133311a(8) =13311313a(9) =31133131a(10) =33113131a(11) =1113131333a(12) =1131131333a(13) =1131311333a(14) =1131331133a(15) =1133111333a(16) =1133113133a(17) =1133133311a(18) =1133311313a(19) =1133313113a(20) =1133313131a(21) =1133331113a(22) =1311113333a(23) =1311311333a(24) =1311313313