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A114740
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Smallest prime == 2n-1 (mod composite(2n-1)), or 0 if impossible.
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0
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5, 3, 5, 7, 41, 11, 13, 0, 17, 19, 0, 23, 101, 67, 29, 31, 131, 137, 37, 151, 41, 43, 109, 47, 463, 0, 53, 0, 137, 59, 61, 0, 0, 67, 163, 71, 73, 0, 0, 79, 0, 83, 317, 677, 89, 457, 0, 347, 97, 0, 101, 103, 0, 107, 109, 257, 113, 419, 271, 431, 439, 1733, 617, 127, 467, 131
(list; graph; refs; listen; history; internal format)
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OFFSET
| 1,1
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EXAMPLE
| a(8)=0 because the 15th composite is 30 and no prime is congruent to 15 (mod 30).
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MATHEMATICA
| f[n_] := Block[{k = 1, m = FixedPoint[2n + PrimePi[ # ] &, 2n - 1]}, While[k < 100000 && Mod[Prime[k], m] != 2n - 1, k++ ]; If[k == 100000, 0, Prime[k]]]; Table[ f[n], {n, 67}] (* Robert G. Wilson v *)
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CROSSREFS
| Sequence in context: A092516 A131925 A128010 * A128008 A144386 A073685
Adjacent sequences: A114737 A114738 A114739 * A114741 A114742 A114743
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KEYWORD
| nonn
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AUTHOR
| Amarnath Murthy (amarnath_murthy(AT)yahoo.com), Nov 15 2005
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EXTENSIONS
| Corrected and extended by Robert G. Wilson v (rgwv(at)rgwv.com), Nov 17 2005
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