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A055385
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Smallest prime factor of n^n + 1.
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6
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2, 5, 2, 257, 2, 13, 2, 97, 2, 101, 2, 89, 2, 29, 2, 274177, 2, 5, 2, 148721, 2, 5, 2, 17, 2, 53, 2, 449, 2, 17, 2, 641, 2, 13, 2, 17, 2, 5, 2, 17, 2, 5, 2, 41, 2, 29, 2, 769, 2, 41, 2, 89, 2, 13, 2, 17, 2, 5, 2, 17, 2, 5, 2, 59649589127497217, 2, 37, 2, 41, 2, 13, 2, 97, 2, 149
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OFFSET
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1,1
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COMMENTS
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If we use the commonly accepted convention that 0^0 = 1, then a(0) = 2. - Chai Wah Wu, Jul 22 2019
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REFERENCES
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C. Stanley Ogilvy and John T. Anderson, Excursions in Number Theory. Dover. New York: 1988. Page 82.
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LINKS
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EXAMPLE
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4^4 + 1 = 257 prime, so a(4) = 257;
6^6 + 1 = 13 * 37 * 97, so a(6) = 13.
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MATHEMATICA
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PROG
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(PARI) a(n) = {if (n % 2, return (2)); return (factor(n^n + 1)[1, 1]); } \\ Michel Marcus, Jul 23 2013
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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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