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A143384 Least a(n) such that M(n)*(M(n)+a(n))-1 is prime with M(i)=i-th Mersenne prime. 2

%I

%S 1,5,1,5,11,11,17,19,23,97,127,145,167,269,767,479,3307,1453,18007,

%T 2357,599,17669,5527,3191,3251,70249,147773,39637

%N Least a(n) such that M(n)*(M(n)+a(n))-1 is prime with M(i)=i-th Mersenne prime.

%C All primes certified using PFGW from Primeform group.

%C M(n) = 2^A000043(n)-1. - _Jens Kruse Andersen_, Jul 30 2014

%e (2^2-1)*(2^2-1+1)-1=11 prime 2^2-1=M(1) so a(1)=1

%e (2^3-1)*(2^3-1+1)-1=55 composite

%e (2^3-1)*(2^3-1+3)-1=69 composite

%e (2^3-1)*(2^3-1+5)-1=83 prime 2^3-1=M(2) so a(2)=5

%Y Cf. A000043 (Mersenne prime exponents), A143385.

%K hard,more,nonn

%O 1,2

%A _Pierre CAMI_, Aug 11 2008

%E Missing terms 2357 and 599 inserted by _Jens Kruse Andersen_, Jul 30 2014

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Last modified January 24 18:53 EST 2022. Contains 350565 sequences. (Running on oeis4.)