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 A175853 #15 Mar 13 2014 02:41:56 %S A175853 20,128768,33501184 %N A175853 (2*n-1)-perfect numbers. %C A175853 For the definition see A175837. %C A175853 Considering only terms of the form 2^k * p with p prime results in a linear equation for p for a given k. Solving quickly generates other terms of the sequence: 137433972736, 2199001235456, 649037107316852462774394019643392, and a 157-digit term associated with k=260. - _D. S. McNeil_, Dec 08 2010 %F A175853 A033880(a(n))=A000005(a(n))/2-1. %e A175853 Proper divisors of 20 are: 1,2,4,5,10. Since 2*20-1=(2*1-1)+(2*2-1)+(2*4-1)+(2*5-1)+(2*10-1)=39, then 20 is in the sequence. %Y A175853 Cf. A175837 (abundant version), A175522, A033880, A000005. %K A175853 nonn,hard,more,bref %O A175853 1,1 %A A175853 _Vladimir Shevelev_, Dec 05 2010 %E A175853 a(3) from _D. S. McNeil_, Dec 08 2010