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

Terms

a(0) =0a(1) =1a(2) =1a(3) =2a(4) =3a(5) =8a(6) =13a(7) =22a(8) =43a(9) =79a(10) =140a(11) =258a(12) =480a(13) =877a(14) =1646a(15) =3083a(16) =5788a(17) =10940a(18) =20623a(19) =39191a(20) =74441a(21) =141826a(22) =270992a(23) =518323a(24) =993869a(25) =1910174a(26) =3674150a(27) =7078905a(28) =13654626a(29) =26375091