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 A172516 #3 Mar 30 2012 17:22:55
%S A172516 2,3,6,10,18,30,60,108,180,360,720,1260,2520,5040,9240,17640,35280,
%T A172516 65520,131040,257040,498960,982800,1884960,3603600,7207200,14414400,
%U A172516 28274400,56548800,110270160,220540320,428828400,845404560,1690809120
%N A172516 Least number k such that sigma(k) >= 2^n.
%C A172516 For n-bit arithmetic, m=a(n)-1 is the largest number for which sigma(m) can be computed without overflow. This is a subsequence of the highly abundant numbers, A002093, which is very useful for computing this sequence. a(63) is 1454751268447276800.
%H A172516 T. D. Noe, <a href="/A172516/b172516.txt">Table of n, a(n) for n=1..64</a>
%F A172516 a(n) <= 2 * a(n-1)
%t A172516 k=1; Table[While[DivisorSigma[1,k]<2^n, k++ ]; k, {n,20}]
%Y A172516 A141847 (least number k such that sigma2(k) >= 2^n)
%K A172516 nonn
%O A172516 1,1
%A A172516 _T. D. Noe_, Feb 05 2010