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Primes of the form p^2 + p - 1 when p is prime.
5

%I #14 Sep 08 2022 08:45:00

%S 5,11,29,131,181,379,991,1721,2861,3539,6971,8009,10301,10711,17291,

%T 22349,26731,32941,36671,37441,39799,54521,58321,69431,79241,109891,

%U 122149,139501,161201,175979,186191,187921,202049,212981,214831,249499

%N Primes of the form p^2 + p - 1 when p is prime.

%C Previous name: Primes produced in A053184.

%H Vincenzo Librandi, <a href="/A053185/b053185.txt">Table of n, a(n) for n = 1..1200</a>

%t Select[#^2 + # - 1 &/@Prime[Range[200]], PrimeQ] (* _Vincenzo Librandi_, Aug 12 2017 *)

%o (PARI) isA053185(n)={local(r);r=0;for(i=floor(sqrt(n+1)),ceil(sqrt(n)-1),if(isprime(i) && n==i^2+i-1 && isprime(n),r=1));r} \\ _Michael B. Porter_, May 10 2010

%o (PARI) lista(nn) = forprime(p=2, nn, if (isprime(q=p^2+p-1), print1(q, ", "))); \\ _Michel Marcus_, Aug 12 2017

%o (Magma) [p: p in PrimesUpTo(600) | IsPrime(p) where p is p^2+p-1]; // _Vincenzo Librandi_, Aug 12 2017

%Y Cf. A053184.

%K easy,nonn

%O 1,1

%A _Enoch Haga_, Mar 01 2000

%E New name from _Michel Marcus_, Aug 12 2017