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A116895
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Least prime factor of n^n-1.
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3
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3, 2, 3, 2, 5, 2, 3, 2, 3, 2, 5, 2, 3, 2, 3, 2, 7, 2, 3, 2, 3, 2, 5, 2, 3, 2, 3, 2, 7, 2, 3, 2, 3, 2, 5, 2, 3, 2, 3, 2, 13, 2, 3, 2, 3, 2, 5, 2, 3, 2, 3, 2, 5, 2, 3, 2, 3, 2, 7, 2, 3, 2, 3, 2, 5, 2, 3, 2, 3, 2, 5, 2, 3, 2, 3, 2, 7, 2, 3, 2, 3, 2, 5, 2, 3, 2, 3, 2, 7, 2, 3, 2, 3, 2, 5, 2, 3, 2, 3, 2, 7, 2
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OFFSET
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2,1
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COMMENTS
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If n is odd then a(n)=2; also, if n is even and not divisible by 3 then a(n)=3. - Zak Seidov, Mar 03 2006
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LINKS
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Antti Karttunen, Table of n, a(n) for n = 2..16384
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EXAMPLE
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6^6-1=5*7*31*43, so a(6)=5.
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MATHEMATICA
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Table[FactorInteger[GCD[n^n-1, 200! ]][[1, 1]], {n, 2, 130}]
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PROG
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(PARI) A116895(n) = { my(k=(n^n)-1); forprime(p=2, , if(!(k%p), return(p))); }; \\ Antti Karttunen, Dec 19 2018
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CROSSREFS
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Cf. A006486, A007571, A048861.
Sequence in context: A066919 A268714 A084117 * A134267 A249800 A165258
Adjacent sequences: A116892 A116893 A116894 * A116896 A116897 A116898
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KEYWORD
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nonn
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AUTHOR
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Giovanni Resta, Mar 02 2006
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STATUS
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approved
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