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%I #9 Sep 08 2022 08:45:25
%S 1,155,341,505,1331,1639,1805,2755,3421,5255,6161,6805,7831,10505,
%T 11341,11771,12655,18631,22649,24491,26405,27721,29755,31861,36289,
%U 37055,39401,44309,49505,51301,52211,54055,56881,62749,65791,68905,73169
%N p^2-p-1 that is not prime, where p is prime.
%C All prime factors of a(n) {5,11,19,29,31,41,59,61,..} belong to A038872 Primes congruent to {0, 1, 4} mod 5. Also odd primes where 5 is a square mod p. A091568 Primes of the form p^2-p-1, where p is prime. A091567 Primes p such that p^2-p-1 is prime.
%H Vincenzo Librandi, <a href="/A119609/b119609.txt">Table of n, a(n) for n = 1..1000</a>
%t lst = {}; Do[If[PrimeQ[p] && ! PrimeQ[p^2 - p - 1], AppendTo[lst, p^2 - p -1]], {p, 300}]; lst (* _Vincenzo Librandi_, Sep 08 2012 *)
%o (Magma) [q: p in PrimesUpTo(300) | IsPrime(p) and not IsPrime(q) where q is p^2 - p - 1] // _Vincenzo Librandi_, Sep 08 2012
%Y Cf. A091568, A091567, A038872.
%K nonn
%O 1,2
%A _Alexander Adamchuk_, Jul 27 2006
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