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A130074
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Nonprimes k such that k divides 5^k - 3^k - 2^k = A130072(k).
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5
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1, 4, 6, 8, 9, 12, 15, 16, 18, 24, 25, 27, 32, 36, 44, 45, 48, 54, 64, 72, 75, 81, 95, 96, 108, 125, 128, 133, 135, 144, 162, 175, 192, 216, 225, 243, 256, 264, 288, 324, 325, 361, 375, 384, 405, 432, 475, 486, 512, 561, 576, 594, 618, 625, 648, 675, 704, 729, 768
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OFFSET
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1,2
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COMMENTS
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Numbers k such that k divides A130072(k) are listed in A130073(n) = {1,2,3,4,5,6,7,8,9,11,12,13,15,16,17,18,19,23,24,25,27,29,31,32,36,37,41,43,...}, which includes all primes. a(n) includes nonprimes in A130073(n). p^(k+1) divides A130072(p^k) for prime p = {2,3,5,19} = A130076(n) and all k>0. It appears that a(n) includes all powers p^k of primes p = {2,3,5,19} for k>1 and all powers of numbers of the form 2^k*3^m, 3^k*5^m, 5^k*19^m.
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LINKS
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MATHEMATICA
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Select[Range[10000], !PrimeQ[ # ]&&IntegerQ[(PowerMod[5, #, # ]-PowerMod[3, #, # ]-PowerMod[2, #, # ])/# ]&]
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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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