A321582 - OEIS

%I #16 Dec 24 2018 08:56:43

%S 241,421,541,571,751,1171,1291,1621,1861,2011,2221,2251,2341,2521,

%T 2671,2851,2971,3271,3361,3391,3541,3571,3691,4021,4201,4591,4621,

%U 4861,5641,5701,5821,6211,6961,7321,7351,7591,7951,8101,8161,8191,8221,8821,8971,9151,9241,9421

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

%C Subsequence of A320774.

%H Seiichi Manyama, <a href="/A321582/b321582.txt">Table of n, a(n) for n = 1..10000</a>

%e 241 is a term since it is prime and (4*241+1)/5 = 193, prime.

%p for n from 4 to 1000 do

%p Y := ithprime(n);

%p Z := 4*Y+1;

%p K := (1/5)*Z;

%p if mod(Z, 5) = 0 and isprime(K) then print(Y);

%p end if:

%p end do:

%t Select[Prime[Range[1000]], PrimeQ[(4 # + 1)/5] &] (* _Amiram Eldar_, Nov 13 2018 *)

%Y Cf. A320774.

%K nonn

%O 1,1

%A _David James Sycamore_, Nov 13 2018

%E More terms from _Seiichi Manyama_, Dec 24 2018