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%I #3 Mar 31 2012 13:22:05
%S 2,21,23,80,96,111,168,230,281,347,558,704
%N Greatest integer M(i)=n such that A085427(n)=A085427(n-1)/2 and k(i+1)>k(i) with A085427(n)=least k such that k*2^n-1 is prime ( Mersenne prime when k=1).
%e A085427 =3,2,1,1,2,1,2,1,5,7,5,3,2,1,5,4,2,1,2,1,14,7,26,13,39,22
%e A(2)=1,A(1)=2 so A(2)=A(1)/2 so M(1)=1
%e A(5)=1,A(4)=2 but A(5)=A(2) ..........
%e A(21)=7,A(20)=14 A(21)=A(20)/2 and A(21)>A(2) so M(2)=21
%Y Cf. A087425, A135054.
%K nonn,uned
%O 1,1
%A _Pierre CAMI_, Nov 15 2007