Primes formed by concatenating k, k, and 7.

Terms

a(0) =227a(1) =337a(2) =557a(3) =887a(4) =997a(5) =11117a(6) =24247a(7) =26267a(8) =27277a(9) =29297a(10) =30307a(11) =32327a(12) =39397a(13) =48487a(14) =51517a(15) =54547a(16) =60607a(17) =62627a(18) =65657a(19) =68687a(20) =69697a(21) =72727a(22) =74747a(23) =78787a(24) =81817a(25) =87877a(26) =89897a(27) =90907a(28) =92927a(29) =93937