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 A243455 #15 Jul 17 2019 04:20:03 %S A243455 6,61,2089,3606,18585,28710,70981,121374,176529,520320,970783, %T A243455 62788800,114682878,144653952,174635334,182054895,3857228169, %U A243455 4349012190,15994971740,17587660602,22842677823,65183331200,66928439760 %N A243455 Numbers n such that (n, sigma(n), tau(n)) lies on a sphere with integral radius centered at the origin, i.e., n^2 + sigma(n)^2 + tau(n)^2 is a square. %C A243455 a(17) > 3*10^9. - _Jinyuan Wang_, Jul 09 2019 %C A243455 a(24) > 10^12, if it exists. - _Giovanni Resta_, Jul 17 2019 %e A243455 6^2 + tau(6)^2 + sigma(6)^2 = 36 + 16 + 144 = 196 = 14^2. So 6 is in the sequence. %o A243455 (PARI) isok(n) = issquare(n^2 + numdiv(n)^2 + sigma(n)^2); %Y A243455 Cf. A000005 (tau), A000203 (sigma), A066764 (analog in 2d). %K A243455 nonn,more %O A243455 1,1 %A A243455 _Michel Marcus_, Jun 05 2014 %E A243455 a(13)-a(16) from _Jinyuan Wang_, Jul 09 2019 %E A243455 a(17)-a(23) from _Giovanni Resta_, Jul 17 2019