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 A062572 Numbers k such that 6^k - 5^k is prime. 110
 2, 5, 11, 13, 23, 61, 83, 421, 1039, 1511, 31237, 60413, 113177, 135647, 258413 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,1 COMMENTS The 809- and 1176-digit numbers associated with the terms 1039 and 1511 have been certified prime with Primo. - Rick L. Shepherd, Nov 15 2002 LINKS Table of n, a(n) for n=1..15. EXAMPLE 2 is in the sequence because 6^2 - 5^2 = 36 - 25 = 11, which is prime. 3 is not in the sequence because 6^3 - 5^3 = 216 - 125 = 91 = 7 * 13, which is not prime. MATHEMATICA Select[Range[1000], PrimeQ[6^# - 5^#] &] (* Alonso del Arte, Sep 04 2013 *) PROG (PARI) forprime(p=2, 1e4, if(ispseudoprime(6^n-5^n), print1(p", "))) \\ Charles R Greathouse IV, Jun 10 2011 CROSSREFS Cf. A000043, A057468, A059801, A059802, A062573-A062666. Sequence in context: A113305 A095078 A335874 * A215214 A221868 A220141 Adjacent sequences: A062569 A062570 A062571 * A062573 A062574 A062575 KEYWORD nonn,hard,more AUTHOR Mike Oakes, May 18 2001, May 19 2001 EXTENSIONS Edited by T. D. Noe, Oct 30 2008 Two more terms (31237 and 60413) found by Predrag Minovic in 2004 corresponding to probable primes with 24308 and 47011 digits. Jean-Louis Charton, Oct 06 2010 Two more terms (113177 and 135647) found by Jean-Louis Charton in 2009 corresponding to probable primes with 88069 and 105554 digits. Jean-Louis Charton, Oct 13 2010 a(15) from Jean-Louis Charton, Apr 08 2013 STATUS approved

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Last modified December 1 21:21 EST 2023. Contains 367502 sequences. (Running on oeis4.)