# Greetings from The On-Line Encyclopedia of Integer Sequences! http://oeis.org/

Search: id:a034923
Showing 1-1 of 1

%I A034923 #35 Nov 27 2024 10:34:32
%S A034923 4,6,42,64,65,1017,3390,3894,8904,12976
%N A034923 Numbers k such that 43^k - 42 is prime.
%C A034923 Related to hyperperfect numbers of a certain form.
%C A034923 k = 1017 produces a 1662-digit number which is only a probable prime. Any additional terms are greater than 1500.
%C A034923 a(7) > 3000. - _Vincenzo Librandi_, Sep 27 2012
%C A034923 a(11) > 50000. - _Michael S. Branicky_, Nov 27 2024
%H A034923 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 A034923 Select[Range[1500], PrimeQ[43^# - 42] &] (* _Vincenzo Librandi_, Sep 27 2012 *)
%o A034923 (PARI) for(n=2,1500, if(isprime(43^n-42), print1(n,",")))
%K A034923 nonn,more
%O A034923 1,1
%A A034923 _Jud McCranie_
%E A034923 a(6) from _Rick L. Shepherd_, Jun 21 2002
%E A034923 a(7)-a(8) from _Michael S. Branicky_, Aug 15 2021
%E A034923 a(9)-a(10) from _Michael S. Branicky_, Mar 28 2023

# Content is available under The OEIS End-User License Agreement: http://oeis.org/LICENSE