This is a front-end for the Online Encyclopedia of Integer Sequences, made by Christian Perfect. The idea is to provide OEIS entries in non-ancient HTML, and then to think about how they're presented visually. The source code is on GitHub.
%I A303449 #16 Apr 24 2018 23:15:10 %S A303449 1,7,31,127,511,2047,8191,32767,131071,524287,299593,8388607,33554431, %T A303449 134217727,536870911,2147483647,8589934591,34359738367,137438953471, %U A303449 549755813887,2199023255551,8796093022207,35184372088831,140737488355327,562949953421311,2251799813685247 %N A303449 Denominator of (2*n+1)/(2^(2*n+1)-1). %C A303449 If A160145(n) = 0, then a(n) = A083420(n). %C A303449 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 A303449 seq(denom((2*n+1)/(2^(2*n+1)-1)), n=0..25); %o A303449 (PARI) a(n) = denominator((2*n+1)/(2^(2*n+1)-1)); %o A303449 (PARI) forstep(k=1, 1e2, 2, print1(denominator(k/(2^k-1)), ", ")); %Y A303449 Cf. A005408, A036259, A083420, A160144 (numerators), A160145. %K A303449 nonn,easy,frac %O A303449 0,2 %A A303449 _Altug Alkan_, Apr 24 2018