%I #16 Apr 24 2018 23:15:10
%S 1,7,31,127,511,2047,8191,32767,131071,524287,299593,8388607,33554431,
%T 134217727,536870911,2147483647,8589934591,34359738367,137438953471,
%U 549755813887,2199023255551,8796093022207,35184372088831,140737488355327,562949953421311,2251799813685247
%N Denominator of (2*n+1)/(2^(2*n+1)-1).
%C If A160145(n) = 0, then a(n) = A083420(n).
%C Least values of k such that a(k) = A083420(k)/A036259(n) are 0, 10, 126, 77, 540, 73, 1242, 328, 1540, 489 for 1 <= n <= 10.
%p seq(denom((2*n+1)/(2^(2*n+1)-1)), n=0..25);
%o (PARI) a(n) = denominator((2*n+1)/(2^(2*n+1)-1));
%o (PARI) forstep(k=1, 1e2, 2, print1(denominator(k/(2^k-1)), ", "));
%Y Cf. A005408, A036259, A083420, A160144 (numerators), A160145.
%K nonn,easy,frac
%O 0,2
%A _Altug Alkan_, Apr 24 2018