Number of Sophie Germain primes less than 2^n.

Terms

a(0) =0a(1) =2a(2) =3a(3) =4a(4) =6a(5) =8a(6) =11a(7) =18a(8) =26a(9) =39a(10) =62a(11) =103a(12) =170a(13) =281a(14) =474a(15) =834a(16) =1464a(17) =2555a(18) =4493a(19) =8051a(20) =14499a(21) =26375a(22) =48024a(23) =88175a(24) =161833a(25) =297544a(26) =549330a(27) =1018008a(28) =1893255a(29) =3527324