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 A018883 #9 Mar 30 2012 18:35:08 %S A018883 2,3,12,21,21,21,60,184,184,280,280,364,364,364,1456,3124,3124,5236, %T A018883 5236,5236,5236,17185,17185,25249,25249,25249,25249,49504,49504,49504, %U A018883 49504,49504,49504,49504,49504,233776,233776,233776,233776,364144,364144 %N A018883 Least nonsquare having square residues for all moduli 2 through n. %K A018883 nonn %O A018883 2,1 %A A018883 _David W. Wilson_