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A345705
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Numbers k such that (3^ord(3/2, k) - 2^ord(3/2, k))/k is a prime, where ord(3/2, k) is the multiplicative order of 3/2 (mod k).
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0
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13, 29, 35, 47, 53, 71, 95, 133, 263, 275, 485, 529, 773, 1009, 1261, 1559, 2711, 3767, 4009, 5275, 7613, 8645, 10295, 11605, 21311, 27755, 29927, 40565, 44519, 67135, 67849, 75335, 83333, 105469, 107185, 153557, 164365, 383705, 405623, 420341, 443105
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OFFSET
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1,1
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COMMENTS
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Numbers k such that gcd(k, 6) = 1 and if m is the least positive integer such that k divides 3^m - 2^m, then (3^m - 2^m)/k is a prime number.
The corresponding primes are 5, 71, 19, 2002867877, 29927, 29, 7, 5, ...
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LINKS
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FORMULA
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13 is a term since ord(3/2, 13) = 4 and (3^4 - 2^4)/13 = 5 is a prime number.
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MATHEMATICA
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ord[n_] := Module[{k = 1}, While[! Divisible[PowerMod[3, k, n] - PowerMod[2, k, n], n], k++]; k]; f[k_] := 3^k - 2^k; Select[Range[1000], CoprimeQ[6, #] && PrimeQ[f[ord[#]]/#] &]
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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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