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 A062573 Numbers n such that 7^n - 6^n is prime. 4
 2, 3, 7, 29, 41, 67, 1327, 1399, 2027, 69371, 86689, 355039 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,1 COMMENTS Terms greater than 1000 often correspond only to strong probable primes. LINKS Henri & Renaud Lifchitz, Top probable primes of the form 7^p-6^p EXAMPLE 7^2 - 6^2 = 49 - 36 = 13, which is prime, so 2 is in the sequence. 7^3 - 6^3 = 343 - 216 = 127, which is prime, so 3 is in the sequence. MATHEMATICA Select[Range[100], PrimeQ[7^# - 6^#] &] (* Alonso del Arte, Sep 04 2013 *) PROG (PARI) is(n)=ispseudoprime(7^n-6^n) \\ Charles R Greathouse IV, Feb 20 2017 CROSSREFS Cf. A000043, A057468, A059801, A059802, A062572-A062666. Sequence in context: A270347 A060412 A276665 * A019435 A061092 A084435 Adjacent sequences:  A062570 A062571 A062572 * A062574 A062575 A062576 KEYWORD nonn,hard AUTHOR Mike Oakes, May 18 2001, May 19 2001 EXTENSIONS Two more terms (69371 and 86689) found by Predrag Minovic in 2004 corresponding to probable primes with 58626 and 73261 digits. Jean-Louis Charton, Oct 06 2010 New term 355039 found by Jean-Louis Charton in May 2011 corresponding to a probable prime with 300043 digits. STATUS approved

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Last modified March 28 17:46 EDT 2020. Contains 333100 sequences. (Running on oeis4.)