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 A110337 a(n) = 2n+1 if 2n+1 is prime else a(n) = least prime of the form (2n+1)(2n+3)...(2n+2k-1) + 2. 0
 3, 5, 7, 101, 11, 13, 257, 17, 19, 9454727, 23, 677, 801011, 29, 31, 42737, 1297, 37, 1601, 41, 43, 5285387, 47, 410006013351009077, 148667, 53, 3137, 56284059197, 59, 61, 1529270318745462748663049625086428127, 4357, 67, 26822027, 71, 73 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,1 LINKS EXAMPLE a(4) = 9*11+2= 101, as 9 is composite. PROG (PARI) a(n) = {pr = 2*n+1; if (isprime(pr), return (pr)); pa = pr; ok = 0; while (! ok, pa += 2; pr *= pa; ok = isprime(pr + 2); ); pr + 2; } \\ Michel Marcus, Sep 16 2013 CROSSREFS Cf. A110336. Sequence in context: A051345 A242387 A104388 * A132287 A046201 A292848 Adjacent sequences: A110334 A110335 A110336 * A110338 A110339 A110340 KEYWORD nonn AUTHOR Amarnath Murthy, Jul 20 2005 EXTENSIONS More terms from Victoria Sapko (vsapko(AT)frc.mass.edu), Sep 28 2007 Corrected and extended by Michel Marcus, Sep 16 2013 STATUS approved

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Last modified February 7 12:36 EST 2023. Contains 360116 sequences. (Running on oeis4.)