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 A141847 #6 Dec 24 2016 21:27:13
%S A141847 2,2,3,4,6,8,10,15,20,28,40,54,78,108,156,216,300,420,600,840,1188,
%T A141847 1680,2340,3360,4680,6600,9240,13200,18480,26400,36960,52560,73920,
%U A141847 105000,147840,209160,294840,415800,589680,831600,1178100,1663200,2353680
%N A141847 Least number k such that sigma_2(k) >= 2^n.
%C A141847 For n-bit arithmetic, m=a(n) - 1 is the largest number for which sigma_2(m) can be computed without overflow. For 31, 32, 63 and 64 bits, the numbers are respectively 36959, 52559, 2389186799 and 3380176799.
%H A141847 T. D. Noe, <a href="/A141847/b141847.txt">Table of n, a(n) for n=1..64</a>
%F A141847 For large n, a(n) ~ sqrt(2)*a(n-1).
%t A141847 k=1; Table[While[DivisorSigma[2,k]<2^n, k++ ]; k, {n,40}]
%Y A141847 Cf. A001157 (sigma_2).
%K A141847 nonn
%O A141847 1,1
%A A141847 _T. D. Noe_, Jul 11 2008