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 A028767 #17 Jul 22 2025 13:47:57 %S A028767 2,3,5,6,8,11,12,14,15,17,18,20,21,23,24,26,29,30,32,33,35,38,39,41, %T A028767 42,44,45,47,48,50,51,53 %N A028767 Nonsquares mod 54. %t A028767 Complement[Range[0, 53], PowerMod[Range[54], 2, 54]] (* _Alonso del Arte_, Dec 27 2019 *) %o A028767 (Scala) (0 to 53).diff((1 to 54).map(n => (n * n) % 54)) // _Alonso del Arte_, Dec 27 2019 %o A028767 (Magma) [ n: n in [0..53] | not IsSquare(R! n) where R:= ResidueClassRing(54)]; // _Vincenzo Librandi_, Dec 28 2019 %Y A028767 Cf. A010415, A028740 (subsequence). %K A028767 nonn,fini,full,easy %O A028767 1,1 %A A028767 _N. J. A. Sloane_