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A321582 Primes p such that (4*p+1)/5 is prime.

%I A321582 #16 Dec 24 2018 08:56:43
%S A321582 241,421,541,571,751,1171,1291,1621,1861,2011,2221,2251,2341,2521,
%T A321582 2671,2851,2971,3271,3361,3391,3541,3571,3691,4021,4201,4591,4621,
%U A321582 4861,5641,5701,5821,6211,6961,7321,7351,7591,7951,8101,8161,8191,8221,8821,8971,9151,9241,9421
%N A321582 Primes p such that (4*p+1)/5 is prime.
%C A321582 Subsequence of A320774.
%H A321582 Seiichi Manyama, <a href="/A321582/b321582.txt">Table of n, a(n) for n = 1..10000</a>
%e A321582 241 is a term since it is prime and (4*241+1)/5 = 193, prime.
%p A321582 for n from 4 to 1000 do
%p A321582 Y := ithprime(n);
%p A321582 Z := 4*Y+1;
%p A321582 K := (1/5)*Z;
%p A321582 if mod(Z, 5) = 0 and isprime(K) then print(Y);
%p A321582 end if:
%p A321582 end do:
%t A321582 Select[Prime[Range[1000]], PrimeQ[(4 # + 1)/5] &] (* _Amiram Eldar_, Nov 13 2018 *)
%Y A321582 Cf. A320774.
%K A321582 nonn
%O A321582 1,1
%A A321582 _David James Sycamore_, Nov 13 2018
%E A321582 More terms from _Seiichi Manyama_, Dec 24 2018