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 A059802 Numbers k such that 5^k - 4^k is prime. 111
 3, 43, 59, 191, 223, 349, 563, 709, 743, 1663, 5471, 17707, 19609, 35449, 36697, 45259, 91493, 246497, 265007, 289937 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,1 COMMENTS Some of the larger terms may only correspond to probable primes. 5^1663 - 4^1663, a 1163-digit number, has been certified prime with Primo. - Rick L. Shepherd, Nov 13 2002 4 more terms found by Predrag Minovic in 2004: 35449, 36697, 45259, 91493. Corresponding numbers of decimal digits are 24778, 25651, 31635, 63951. - Alexander Adamchuk, Dec 02 2006 LINKS MATHEMATICA Select[Range[1000], PrimeQ[5^# - 4^#] &] (* Alonso del Arte, Sep 09 2013 *) PROG (PARI) forprime(p=2, 1e5, if(ispseudoprime(5^p-4^p), print1(p", "))) \\ Charles R Greathouse IV, Jun 10 2011 CROSSREFS Cf. A005060. Cf. A000043, A057468, A059801, A128335, etc. Sequence in context: A137192 A253577 A337213 * A139854 A194578 A185632 Adjacent sequences: A059799 A059800 A059801 * A059803 A059804 A059805 KEYWORD nonn,hard AUTHOR Mike Oakes, Feb 23 2001 EXTENSIONS New term 246497 found by Jean-Louis Charton in 2008 corresponding to a probable prime with 172295 digits - Jean-Louis Charton, Sep 02 2009 New term a(19) = 265007 found by Jean-Louis Charton, Feb 19 2013 a(20) = 289937 found by Jean-Louis Charton, Mar 15 2013 STATUS approved

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Last modified March 25 19:21 EDT 2023. Contains 361528 sequences. (Running on oeis4.)