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A137909 Least k such that k*(2^p-1)*(k*(2^p-1)+1)+1 is prime, where 2^p-1 runs through the Mersenne primes. 4

%I

%S 1,2,2,3,17,8,3,6,96,9,224,33,260,1044,2397,3,1487,657,9602,2133,

%T 18438,93,17273,32583,66539,9632,1431,100440,150857

%N Least k such that k*(2^p-1)*(k*(2^p-1)+1)+1 is prime, where 2^p-1 runs through the Mersenne primes.

%e 1*(2^2-1)*(1*(2^2-1)+1)+1=13 prime, 2^2-1 first Mersenne prime, a(1)=1

%e 2*(2^3-1)*(2*(2^3-1)+1)+1=211 prime, 2^3-1 second Mersenne prime, a(2)=2

%Y Cf. A000043 (Mersenne exponents), A000668 (Mersenne primes).

%Y Cf. A137906, A137907, A137908.

%K hard,more,nonn

%O 1,2

%A _Pierre CAMI_, Feb 22 2008

%E a(27)-a(29) by _Pierre CAMI_, Oct 11 2014

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Last modified July 24 23:25 EDT 2021. Contains 346273 sequences. (Running on oeis4.)