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A152533
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Numbers k>4 such that 10^k + 1111 is prime.
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0
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5, 11, 22, 41, 43, 203, 243, 305, 321, 570, 731, 1512, 1787, 2146, 3987, 4056, 5296
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OFFSET
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1,1
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COMMENTS
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The decimal expansion of 10^k + 1111 consists of a single '1' digit followed by k-4 '0' digits followed by four '1' digits. (See Example section.)
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LINKS
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EXAMPLE
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101111 is prime, so 5 is in the sequence;
100000001111 is prime, so 11 is in the sequence.
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PROG
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(PARI) isok(n) = (n > 4) && isprime(10^n+1111); \\ Michel Marcus, Oct 15 2013
(Python)
from sympy import isprime, prime
def afind(limit, startk=5):
k, pow10 = startk, 10**startk
for k in range(startk, limit+1):
if isprime(pow10 + 1111): print(k, end=", ")
pow10 *= 10
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CROSSREFS
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KEYWORD
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nonn,base,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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