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A247229
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Minimum of the greatest prime factors of (i^prime(n)-1)/(i-1), when i runs through all integers in [2, prime(n)].
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1
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3, 7, 11, 127, 89, 8191, 30839, 363889, 178481, 2089, 4404047, 616318177, 164511353, 2099863, 13264529, 20394401
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OFFSET
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1,1
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COMMENTS
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If in the definition "greatest" is replaced with "smallest", then we obtain A035095 (see comment there).
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LINKS
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Table of n, a(n) for n=1..16.
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FORMULA
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a(n) == 1 (mod prime(n)).
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PROG
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(PARI) a(n) = {mini = 0; p = prime(n); for (i=2, p, f = factor((i^p-1)/(i-1)); gpf = f[#f~, 1]; if (! mini, mini = gpf, mini = min(mini, gpf)); ); mini; } \\ Michel Marcus, Dec 09 2014
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CROSSREFS
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Cf. A035095, A247216.
Sequence in context: A287301 A105762 A057469 * A082598 A082599 A354082
Adjacent sequences: A247226 A247227 A247228 * A247230 A247231 A247232
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KEYWORD
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nonn,more
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AUTHOR
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Vladimir Shevelev, Nov 27 2014
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EXTENSIONS
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More terms from Peter J. C. Moses, Nov 27 2014
a(13)-a(14) from Michel Marcus, Dec 09 2014
a(15)-a(16) from Jinyuan Wang, Mar 03 2020
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STATUS
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approved
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