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 A091901 #26 Feb 16 2025 08:32:52 %S A091901 7,11,13,14,15,17,19,21,22,23,25,26,27,28,29,31,32,33,34,35,37,38,39, %T A091901 40,41,42,43,44,45,46,47,49,50,51,52,53,54,55,56,57,58,59,61,62,63,64, %U A091901 65,66,67,68,69,70,71,73,74,75,76,77,78,79,80,81,82,83,85,86,87,88,89 %N A091901 Values of n for which sigma(n) < e^gamma * n * log(log(n)). %C A091901 sigma(n) < e^gamma * n * log(log(n)) is "Robin's inequality" - see A067698. Sequence is cofinite if and only if the Riemann Hypothesis is true. %H A091901 G. Caveney, J.-L. Nicolas, and J. Sondow, <a href="http://www.integers-ejcnt.org/l33/l33.pdf">Robin's theorem, primes, and a new elementary reformulation of the Riemann Hypothesis</a>, Integers 11 (2011), #A33. %H A091901 G. Caveney, J.-L. Nicolas and J. Sondow, <a href="http://arxiv.org/abs/1112.6010">On SA, CA, and GA numbers</a>, Ramanujan J., 29 (2012), 359-384. %H A091901 Eric Weisstein's World of Mathematics, <a href="https://mathworld.wolfram.com/RobinsTheorem.html">Robin's Theorem</a> %F A091901 a(n) = n + 27 for n > 5039, if and only if the Riemann Hypothesis is true. - _Charles R Greathouse IV_, May 31 2011 %t A091901 Select[Range[100], DivisorSigma[1, #] < E^EulerGamma*#*Log[Log[#]] &] (* _Jean-François Alcover_, Oct 30 2012 *) %Y A091901 Cf. A067698. %K A091901 nonn,easy %O A091901 1,1 %A A091901 _Eric W. Weisstein_, Feb 09 2004