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%I #19 Feb 04 2024 01:14:09
%S 2,3,5,11,17,41,53,71,83,131,137,173,197,227,263,281,293,383,431,467,
%T 503,521,563,587,593,617,677,683,701,743,797,827,887,911,977,983,1013,
%U 1061,1091,1151,1163,1181,1277,1307,1361,1481,1511,1523,1553,1607,1613
%N Primes p such that 4p-1 is also prime.
%C For n>1, 4*a(n) is a solution to the equation phi(x-1) - phi(x) = x/2. - _Farideh Firoozbakht_, Dec 17 2014
%H Harry J. Smith, <a href="/A062737/b062737.txt">Table of n, a(n) for n = 1..1000</a>
%p select(n -> isprime(n) and isprime(4*n-1), [2,seq(2*k+1,k=1..1000)]); # _Robert Israel_, Dec 17 2014
%o (PARI) { n=0; forprime (p=2, 10^5, if (isprime(4*p - 1), write("b062737.txt", n++, " ", p); if (n==1000, break)) ) } \\ _Harry J. Smith_, Aug 10 2009
%Y Cf. A005384, A007700, A005382.
%K nonn,easy
%O 1,1
%A _Reiner Martin_, Jul 12 2001
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