a(n) = number of primes p, p <= 2^n, where 2^n + p is prime.

Terms

a(0) =0a(1) =0a(2) =1a(3) =2a(4) =3a(5) =3a(6) =5a(7) =9a(8) =11a(9) =18a(10) =32a(11) =51a(12) =84a(13) =151a(14) =254a(15) =429a(16) =754a(17) =1311a(18) =2377a(19) =4199a(20) =7584a(21) =13785a(22) =24955a(23) =45840a(24) =84002a(25) =153515a(26) =283659a(27) =524648a(28) =976217a(29) =1817659