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 A114740 Smallest prime == 2n-1 (mod composite(2n-1)), or 0 if impossible. 0
 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; text; internal format)
 OFFSET 1,1 LINKS EXAMPLE a(8)=0 because the 15th composite is 30 and no prime is congruent to 15 (mod 30). 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 *) CROSSREFS Sequence in context: A131925 A128010 A185046 * A330523 A361546 A128008 Adjacent sequences: A114737 A114738 A114739 * A114741 A114742 A114743 KEYWORD nonn AUTHOR Amarnath Murthy, Nov 15 2005 EXTENSIONS Corrected and extended by Robert G. Wilson v, Nov 17 2005 STATUS approved

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Last modified April 1 19:13 EDT 2023. Contains 361695 sequences. (Running on oeis4.)