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%I #8 Sep 23 2019 10:20:59
%S 2,2,2,2,5,2,2,3,11,17,2,23,29,3,5,3,43,2,7,17,19,3,11,23,13,19,19,7,
%T 43,23,71,5,19,2,59,11,59,2,47,31,89,5,2,3,19,107,11,71,59,23,29,7,61,
%U 89,2,173,11,17,37,37,31,23,19,2,199,103,59,37,139,17,67,41,43
%N Least prime p such that 3*p*2^n-1 is prime.
%H Pierre CAMI, <a href="/A130325/b130325.txt">Table of n, a(n) for n = 0..500</a>
%e 3*2*2^0-1=5 is prime so for n=0 p=2.
%e 3*2*2^1-1=11 is prime so for n=1 p=2.
%o (PARI) a(n) = my(p=2); while (!isprime(3*p*2^n-1), p=nextprime(p+1)); p; \\ _Michel Marcus_, Sep 23 2019
%Y Cf. A130326, A130327.
%K nonn
%O 0,1
%A _Pierre CAMI_, May 24 2007
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