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A127101
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Numbers k such that k^2 divides 9^k - 1.
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29
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1, 2, 4, 8, 10, 20, 40, 110, 136, 164, 220, 328, 440, 610, 680, 820, 1210, 1220, 1544, 1640, 2420, 2440, 2530, 4840, 5060, 5576, 6710, 7370, 7480, 7720, 9020, 10120, 11810, 13420, 13612, 14008, 14740, 18040, 18632, 19580
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OFFSET
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1,2
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LINKS
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MATHEMATICA
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Select[Range[20000], IntegerQ[(PowerMod[9, #, #^2 ]-1)/#^2 ]&]
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PROG
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(PARI) is(k) = Mod(9, k^2)^k == 1; \\ Amiram Eldar, May 21 2024
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CROSSREFS
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Subset of A068382 (numbers k such that k divides 9^k - 1).
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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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