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Numbers n such that 87^n - 86^n is prime.
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%I #15 Jun 06 2017 14:30:34

%S 2,3,47,44563

%N Numbers n such that 87^n - 86^n is prime.

%C a(5) > 10^5. - _Robert Price_, May 11 2015

%t Select[Prime[Range[PrimePi[1000]]], PrimeQ[87^# - 86^#] &] (* _T. D. Noe_, Aug 15 2012 *)

%o (PARI) is(n)=ispseudoprime(87^n-86^n) \\ _Charles R Greathouse IV_, Jun 06 2017

%K nonn,hard

%O 1,1

%A _Jean-Louis Charton_, Aug 15 2012

%E a(4) from Robert Price (computer run by Adam Marciniec), May 11 2015