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%I #27 Sep 08 2022 08:46:01
%S 41,241,401,601,1801,3121,4201,4801,5441,6121,6841,9241,13001,15121,
%T 17401,19841,21121,22441,23801,26641,29641,32801,45121,47041,51001,
%U 57241,63841,75641,78121,91121,96601,99401,102241,108041,114001,117041
%N Primes of the form 5*k^2 - 4.
%C Also, primes of the form 20*k^2 + 20*k + 1. - _Jan Rider_, May 22 2018
%H Vincenzo Librandi, <a href="/A201786/b201786.txt">Table of n, a(n) for n = 1..5000</a>
%t Select[Table[5n^2-4,{n,1,1000}],PrimeQ]
%o (Magma) [a: n in [1..400] | IsPrime(a) where a is 5*n^2-4];
%o (PARI) lista(nn) = for (n=1, nn, if (isprime(p=5*n^2-4), print1(p, ", "));); \\ _Michel Marcus_, May 22 2018
%Y Cf. A090562, A195317.
%K nonn
%O 1,1
%A _Vincenzo Librandi_, Dec 05 2011
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