Safe primes p: (p-1)/2 is also prime.

Terms

a(0) =5a(1) =7a(2) =11a(3) =23a(4) =47a(5) =59a(6) =83a(7) =107a(8) =167a(9) =179a(10) =227a(11) =263a(12) =347a(13) =359a(14) =383a(15) =467a(16) =479a(17) =503a(18) =563a(19) =587a(20) =719a(21) =839a(22) =863a(23) =887a(24) =983a(25) =1019a(26) =1187a(27) =1283a(28) =1307a(29) =1319