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%I #13 May 26 2018 22:24:00
%S 3,23,95,8063,122879,393215,2146959359,2305843007066210303,
%T 618970017336847128235868159,162258657859193720701440560726015,
%U 170141021201192402518323912137873817599
%N a(n) is the number of positive integers between successive Mersenne primes.
%H Caldwell and Honaker, <a href="https://primes.utm.edu/curios/page.php?number_id=16918">61897...68159 (27-digits)</a>, Prime Curios!
%F a(n) = A139231(n) - 1. - _Omar E. Pol_, Mar 23 2018
%e a(2) = 23 because there are 23 positive integers between successive Mersenne primes 7 and 31.
%t -1 + Differences@ Array[2^MersennePrimeExponent[#] - 1 &, 12] (* _Michael De Vlieger_, Apr 21 2018 *)
%Y Cf. A000668, A139231.
%K nonn
%O 1,1
%A _G. L. Honaker, Jr._, Mar 23 2018