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a(n)= least number k > a(n-1) such that k*(2^p-1)*(k*(2^p-1)+1)-1 is prime, where p = A000043(n) = Mersenne exponents.
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%I #17 Mar 31 2012 13:22:09

%S 1,3,5,7,8,19,20,23,96,190,312,400,434,852,980,1063,1208,3960,5464,

%T 6694,7178,13118,13680,18803,27445,28541,42031,73209,83873

%N a(n)= least number k > a(n-1) such that k*(2^p-1)*(k*(2^p-1)+1)-1 is prime, where p = A000043(n) = Mersenne exponents.

%C a(n) is not so far from p

%C All certified primes using PFGW64 from primeform group

%Y Cf. A000043, A121370

%K nonn

%O 1,2

%A _Pierre CAMI_, Nov 21 2011