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If P(n) is the product of the first n Mersenne primes, then a(n) is the smallest positive integer such that 2*a(n)*P(n)-1 is prime.
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%I #4 Mar 31 2012 10:29:22

%S 1,1,1,8,1,12,4,33,3,19,22,71,58,10,230,1487,2887,555,1260,1711,377,

%T 343

%N If P(n) is the product of the first n Mersenne primes, then a(n) is the smallest positive integer such that 2*a(n)*P(n)-1 is prime.

%C a(2) starts sequence A092527

%e a(4) = 8: 2*8*(2^2-1)*(2^3-1)*(2^5-1)*(2^7-1)-1 = 2*8*3*7*31*127-1 = 1322832-1 = 1322831, which is prime.

%K nonn

%O 1,4

%A _Ray G. Opao_, Apr 12 2004