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Primes of the form 2*s - 1, where s is a squarefree number (A005117).
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%I #8 Feb 22 2021 03:16:41

%S 3,5,11,13,19,29,37,41,43,59,61,67,73,83,101,109,113,131,137,139,157,

%T 163,173,181,193,211,227,229,257,277,281,283,307,313,317,331,347,353,

%U 373,379,389,397,401,409,419,421,433,443,457

%N Primes of the form 2*s - 1, where s is a squarefree number (A005117).

%H Amiram Eldar, <a href="/A066652/b066652.txt">Table of n, a(n) for n = 1..10000</a>

%e a(10) = A000040(17) = 59 = 2*30-1 = 2*A005117(19)-1.

%t Select[2 * Select[Range[200], SquareFreeQ] - 1, PrimeQ] (* _Amiram Eldar_, Feb 22 2021 *)

%Y Cf. A005383, A066651, A066653.

%K nonn

%O 1,1

%A _Reinhard Zumkeller_, Jan 10 2002