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A175148
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a(n) = number of primes p, p <= 2^n, where 2^n + p is composite.
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1
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0, 1, 1, 2, 3, 8, 13, 22, 43, 79, 140, 258, 480, 877, 1646, 3083, 5788, 10940, 20623, 39191, 74441, 141826, 270992, 518323, 993869, 1910174, 3674150, 7078905, 13654626, 26375091, 51007193, 98748888, 191381911
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OFFSET
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0,4
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COMMENTS
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LINKS
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FORMULA
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PROG
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(Python)
from sympy import isprime, primerange
def a(n):
t = 2**n
return sum(1 for p in primerange(2, t+1) if not isprime(t + p))
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CROSSREFS
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KEYWORD
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more,nonn
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AUTHOR
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EXTENSIONS
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STATUS
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approved
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