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A336347
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Least prime factor of 44745755^4*2^(4n+2) + 1.
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2
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13, 101, 29, 13, 39877, 41, 13, 37, 18661, 13, 41, 73, 13, 5719237, 144341, 13, 29, 89, 13, 353, 41, 13, 64450569241, 29, 13, 37, 101, 13, 89, 53, 13, 113, 313, 13, 37, 41, 13, 29, 73, 13, 41, 181, 13, 37, 29, 13, 857, 73, 13, 389, 41, 13, 37
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OFFSET
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0,1
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COMMENTS
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There are k such that k*2^m + 1 is not prime for any m (then k is called a Sierpiński number). Erdős once conjectured that for such a k, the smallest prime factor of k*2^m + 1 would be bounded as m tends to infinitiy. The proven Sierpiński number k=44745755^4 is thought to be the first counterexample to this conjecture.
This sequence is either unbounded (in which case 44745755^4 is in fact a counterexample) or periodic.
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CROSSREFS
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KEYWORD
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nonn
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AUTHOR
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STATUS
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approved
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