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A103795
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Minimal base b such that (b^prime(n)+1)/(b+1) is prime.
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11
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2, 2, 2, 2, 2, 2, 2, 2, 7, 2, 16, 61, 2, 6, 10, 6, 2, 5, 46, 18, 2, 49, 16, 70, 2, 5, 6, 12, 92, 2, 48, 89, 30, 16, 147, 19, 19, 2, 16, 11, 289, 2, 12, 52, 2, 66, 9, 22, 5, 489, 69, 137, 16, 36, 96, 76, 117, 26, 3, 159, 10, 16, 209, 2, 16, 23, 273, 2, 460, 22, 3, 36, 28, 329, 43, 69, 86
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OFFSET
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2,1
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COMMENTS
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Conjecture: sequence is defined for any n>=2.
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LINKS
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FORMULA
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EXAMPLE
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(2^prime(2)+1)/(2+1) = 3 is prime, so a(2)=2;
(2^prime(10)+1)/(2+1) = 178956971 has a factor of 59;
(3^prime(10)+1)/(3+1) = 17157594341221 has a factor of 523;
...
(7^prime(10)+1)/(7+1) = 402488219476647465854701 is prime, so a(10)=7.
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MATHEMATICA
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Do[p=Prime[k]; n=2; cp=(n^p+1)/(n+1); While[!PrimeQ[cp], n=n+1; cp=(n^p+1)/(n+1)]; Print[n], {k, 2, 200}]
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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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