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A216487
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Smallest prime factor of n^(2n) - 1 having the form k*n+1.
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1
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3, 7, 5, 11, 7, 29, 17, 19, 11, 23, 13, 53, 29, 31, 17, 10949, 19, 108301, 41, 43, 23, 47, 73, 101, 53, 109, 29, 59, 31, 373, 257, 67, 103, 71, 37, 149, 191, 79, 41, 83, 43, 173, 89, 181, 47, 659, 97, 197, 101, 103, 53, 991313, 271, 881, 113, 4561, 349, 709
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OFFSET
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2,1
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COMMENTS
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The corresponding values of k are in A216506.
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LINKS
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FORMULA
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EXAMPLE
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a(7) = 29 because 7^14 - 1 = 2 ^ 4 * 3 * 29 * 113 * 911 * 4733 and the smallest prime divisor of the form k*n+1 is 29 = 4*7+1.
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MATHEMATICA
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Table[p=First/@FactorInteger[n^(2*n)-1]; Select[p, Mod[#1, n] == 1 &, 1][[1]], {n, 2, 41}]
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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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