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 A058542 #5 Jun 01 2016 11:10:22 %S A058542 16,17,33,51,81,122,180,-6,-30,-162,-849,-3683,-14889,-67387,-270481, %T A058542 -1083495,-5351733,-23785493,-95779647,-425687333,-1702749333, %U A058542 -7385743647,-33685755741,-156526119063,-703401325293,-3048080581927,-12307998348021,-53348118829343 %N A058542 Trajectory of 16 under map that sends x to 3x - sigma(x). %t A058542 NestList[3#-DivisorSigma[1,#]&,16,30] (* _Harvey P. Dale_, Jun 01 2016 *) %Y A058542 Cf. A037159, A058541, A058545. %K A058542 sign %O A058542 0,1 %A A058542 _N. J. A. Sloane_, Dec 24 2000