Primes p == 3, 9, 11 (mod 20) such that 2p+1 is also prime.

Terms

a(0) =3a(1) =11a(2) =23a(3) =29a(4) =83a(5) =89a(6) =131a(7) =191a(8) =251a(9) =431a(10) =443a(11) =491a(12) =509a(13) =683a(14) =743a(15) =809a(16) =911a(17) =1031a(18) =1049a(19) =1103a(20) =1223a(21) =1229a(22) =1289a(23) =1409a(24) =1451a(25) =1511a(26) =1583a(27) =1811a(28) =1889a(29) =1931