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A175147
a(n) = number of primes p, p <= 2^n, where 2^n + p is prime.
1
0, 0, 1, 2, 3, 3, 5, 9, 11, 18, 32, 51, 84, 151, 254, 429, 754, 1311, 2377, 4199, 7584, 13785, 24955, 45840, 84002, 153515, 283659, 524648, 976217, 1817659, 3392835, 6348677, 11898310
OFFSET
0,4
COMMENTS
Terms through a(18) calculated by M. F. Hasler. Terms through a(29) calculated by Rick Shepherd.
FORMULA
a(n) = A007053(n) - A175148(n).
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
Sequence in context: A296588 A065460 A241741 * A001180 A228778 A296674
KEYWORD
more,nonn
AUTHOR
Leroy Quet, Feb 24 2010
EXTENSIONS
a(30)-a(32) from Ray Chandler, Mar 05 2010
STATUS
approved