Number of Sophie Germain primes <= prime(2^n).

Terms

a(0) =2a(1) =3a(2) =4a(3) =8a(4) =12a(5) =20a(6) =32a(7) =54a(8) =94a(9) =170a(10) =297a(11) =549a(12) =1017a(13) =1895a(14) =3505a(15) =6577a(16) =12388a(17) =23565a(18) =44891a(19) =85922a(20) =164299a(21) =314173a(22) =602624a(23) =1158231a(24) =2232286