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A128400
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Numbers k such that k^2 divides 20^k - 1.
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18
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OFFSET
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1,2
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COMMENTS
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19 divides a(n) for n > 1.
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LINKS
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PROG
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(PARI) for( n=1, 10^6, Mod(20, n^2)^n - 1 || print1(n", ")) \\ M. F. Hasler, Oct 20 2008
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CROSSREFS
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Cf. A128360, A127103, A127104, A127105, A127106, A127107, A127102, A127101, A127100, A127092, A128405, A128393, A128394, A128395, A128396, A128397, A128398, A128399, A128400, A128401, A128402, A128403, A128404.
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KEYWORD
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nonn,hard,more
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AUTHOR
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EXTENSIONS
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STATUS
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approved
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