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A109137
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Numbers k such that k * (10^k - 1) + 1 is prime.
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0
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OFFSET
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1,1
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COMMENTS
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Larger values certified with ECM. No more up to 6000.
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LINKS
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PROG
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(Python)
from sympy import isprime
def afind(limit, startk=1):
k, pow10 = startk, 10**startk
for k in range(startk, limit+1):
if isprime(k*(pow10 - 1) + 1): print(k, end=", ")
k += 1
pow10 *= 10
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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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