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 A114780 Least multiple of 2n-1 ending in prime(n), 0 if no such number exists. 2
 2, 3, 5, 7, 711, 913, 117, 0, 323, 1729, 231, 437, 0, 243, 1247, 1953, 759, 0, 3367, 3471, 2173, 2279, 0, 4089, 2597, 28101, 45103, 0, 2109, 18113, 43127, 40131, 0, 1139, 22149, 34151, 37157, 0, 13167, 62173, 37179, 17181, 0, 38193, 33197, 17199, 86211 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,1 COMMENTS If prime(n) has k digits then a(n) == prime(n) (mod 10^k); a(8r+5) = 0 for r > 1. LINKS EXAMPLE a(5) = 711, ending in 11 = prime(n) and 711 == 0 (mod 9, the fifth odd number). PROG (PARI) a(n) = {if (((n >=8) && ((n-8) % 5 == 0)), return (0)); k = 1; tn = 2*n-1; p = prime(n); tp = 10^length(Str(p)); while ((k*tn) % tp != p, k++); return (k*tn); } \\ Michel Marcus, Sep 15 2013 CROSSREFS Cf. A114781. Sequence in context: A046477 A145843 A090720 * A241681 A134811 A046479 Adjacent sequences:  A114777 A114778 A114779 * A114781 A114782 A114783 KEYWORD base,nonn AUTHOR Amarnath Murthy, Nov 17 2005 EXTENSIONS More terms from Joshua Zucker, May 05 2006 STATUS approved

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Last modified July 3 16:27 EDT 2022. Contains 355055 sequences. (Running on oeis4.)