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 A204940 Numbers n such that (23^n - 1)/22 is prime. 1
 5, 3181, 61441, 91943, 121949 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,1 COMMENTS No other terms < 100000. LINKS H. Lifchitz, Mersenne and Fermat primes field MATHEMATICA Select[Prime[Range[100]], PrimeQ[(23^#-1)/22]&] PROG (PARI) is(n)=ispseudoprime((23^n-1)/22) \\ Charles R Greathouse IV, Jun 13 2017 CROSSREFS Cf. A028491, A004061, A004062, A004063, A004023, A004064, A016054, A006032, A006033, A006034, A006035, A127995, A127996, A127997, A127998, A127999, A128000, A098438, A128002, A128003, A128004, A128005. Sequence in context: A171980 A013782 A137841 * A172954 A079173 A073826 Adjacent sequences:  A204937 A204938 A204939 * A204941 A204942 A204943 KEYWORD hard,nonn,more AUTHOR Robert Price, Jan 20 2012 EXTENSIONS a(5)=121949 corresponds to a probable prime discovered by Paul Bourdelais, Oct 19 2017 STATUS approved

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Last modified December 16 03:14 EST 2019. Contains 330013 sequences. (Running on oeis4.)