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A309741
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Numbers k such that 6*10^(2*k) + 6*10^k + 1 is prime.
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1
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OFFSET
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1,3
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LINKS
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EXAMPLE
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13 is prime. ==> a(1) = 0.
661 is prime. ==> a(2) = 1.
60601 is prime. ==> a(3) = 2.
6006001 = 2027 * 2963.
600060001 is prime. ==> a(4) = 4.
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PROG
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(PARI) for(k=0, 1e3, if(ispseudoprime(6*100^k+6*10^k+1), print1(k", ")))
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CROSSREFS
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KEYWORD
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nonn,more,base,changed
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AUTHOR
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EXTENSIONS
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STATUS
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approved
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