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%I #25 May 12 2021 03:05:42
%S 5,11,13,53,115,899,2287
%N Numbers k such that 47^k-46 is prime.
%C Related to hyperperfect numbers of a certain form.
%H J. S. McCranie, <a href="https://cs.uwaterloo.ca/journals/JIS/VOL3/mccranie.html">A study of hyperperfect numbers</a>, J. Int. Seqs. Vol. 3 (2000) #P00.1.3.
%t Select[Range[2000], PrimeQ[47^# - 46] &] (* _Vincenzo Librandi_, Sep 26 2012 *)
%o (PARI) is(n)=ispseudoprime(47^n-46) \\ _Charles R Greathouse IV_, Jun 13 2017
%o (Python)
%o from sympy import isprime
%o def afind(limit, startat=1):
%o pow47 = 47**startat
%o for k in range(startat, limit+1):
%o if isprime(pow47 - 46): print(k, end=", ")
%o pow47 *= 47
%o afind(900) # _Michael S. Branicky_, May 11 2021
%K nonn,more
%O 1,1
%A _Jud McCranie_
%E a(6) from _Vincenzo Librandi_, Sep 26 2012
%E a(7) from _Michael S. Branicky_, May 11 2021
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