%I #12 Feb 20 2023 14:49:08
%S 0,1,1,2,3,8,13,22,43,79,140,258,480,877,1646,3083,5788,10940,20623,
%T 39191,74441,141826,270992,518323,993869,1910174,3674150,7078905,
%U 13654626,26375091,51007193,98748888,191381911
%N a(n) = number of primes p, p <= 2^n, where 2^n + p is composite.
%C Terms through a(18) calculated by _M. F. Hasler_.
%F a(n) = A007053(n) - A175147(n).
%o (Python)
%o from sympy import isprime, primerange
%o def a(n):
%o t = 2**n
%o return sum(1 for p in primerange(2, t+1) if not isprime(t + p))
%o print([a(n) for n in range(20)]) # _Michael S. Branicky_, Feb 20 2023
%Y Cf. A007053, A175147.
%K more,nonn
%O 0,4
%A _Leroy Quet_, Feb 24 2010
%E a(19)-a(32) from _Ray Chandler_, Mar 05 2010