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 A215509 #6 Aug 14 2012 09:15:59 %S A215509 1,3,4,7,6,13,8,15,13,21,12,31,14,31,26,31,18,49,20,63,32,45,24,65,31, %T A215509 49,40,57,30,91,32,63,52,63,48,91,38,75,56,93,42,127,44,93,121,93,48, %U A215509 127,57,93,80,105,54,121,72,127,80,105,60,217,62,127,104 %N A215509 Numerator of sigma(n)/n when n belongs to A162657. %C A215509 When p is prime, A162657(p)=p so a(p)=p+1. %H A215509 Michel Marcus, <a href="/A215509/b215509.txt">Table of n, a(n) for n = 1..1000</a> %e A215509 A162657(2) = 2, so a(2)=numerator(sigma(2)/2)=numerator(3/2)=3. %Y A215509 Equal to or greater than A214409. %K A215509 nonn %O A215509 1,2 %A A215509 _Michel Marcus_, Aug 14 2012