OFFSET
0,4
COMMENTS
Terms through a(18) calculated by M. F. Hasler. Terms through a(29) calculated by Rick Shepherd.
PROG
(Python)
from sympy import isprime, primerange
def a(n):
t = 2**n
return sum(1 for p in primerange(2, t+1) if isprime(t + p))
print([a(n) for n in range(20)]) # Michael S. Branicky, Feb 20 2023
CROSSREFS
KEYWORD
more,nonn
AUTHOR
Leroy Quet, Feb 24 2010
EXTENSIONS
a(30)-a(32) from Ray Chandler, Mar 05 2010
STATUS
approved