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 A110108 #5 Aug 29 2012 12:43:56 %S A110108 3,9,15,21,27,39,57,63,81,93,105,117,165,171,183,189,201,219,225,243, %T A110108 256,279,303,309,333,351,363,375,381,387,405,417,441,453,471,489,512, %U A110108 543,549,567,579,603,633,651,657,669,687,693,723,729,741,777 %N A110108 Conjectured values of n such that sigma(n)+sigma(k)=sigma(n+k) has no solution. %C A110108 All k<10^10 have been checked. Note that this sequence appears to contain all powers of 3. It also contains 256 and 512, which are the only even numbers listed here. %C A110108 All k<10^11 have been checked. 65 n values remain < 1000. - _Donovan Johnson_, Aug 29 2012 %D A110108 R. K. Guy, Unsolved Problems in Number Theory, 3rd Ed., New York, Springer-Verlag, 2004, Section B15. %Y A110108 Cf. A066435 (least k such that sigma(n)+sigma(k)=sigma(n+k)). %K A110108 nonn %O A110108 1,1 %A A110108 _T. D. Noe_, Jul 12 2005 %E A110108 Two terms removed (465 and 711) by _Donovan Johnson_, Aug 29 2012