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A138578
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Numbers k such that 2^(2*k-7)-7 is prime.
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0
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OFFSET
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1,1
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LINKS
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EXAMPLE
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2^(2*23-7) - 7 = 549755813881 is prime.
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PROG
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(Python)
from sympy import isprime
def afind(limit):
k = 5; pow2 = 2**(2*k-7)
while k < limit:
while not isprime(pow2 - 7) and k <= limit: k += 1; pow2 *= 4
if k > limit: return
print(k, end=", "); k += 1; pow2 *= 4
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CROSSREFS
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KEYWORD
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nonn,more
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AUTHOR
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EXTENSIONS
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STATUS
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approved
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