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 A028754 #15 May 01 2020 23:04:55 %S A028754 3,6,7,11,12,13,14,15,17,19,22,24,26,27,28,29,30,34,35,38 %N A028754 Nonsquares mod 41. %e A028754 x^2 = 7 mod 41 has no solutions, so 7 is in the sequence. %e A028754 x^2 = 8 mod 41 has the solutions x = 7 and x = 34. Hence 8 is not in the sequence. %t A028754 Complement[Range[40], PowerMod[Range[41], 2, 41]] (* _Alonso del Arte_, Jan 12 2017 *) %o A028754 (Scala) (0 to 40).diff((1 to 41).map(n => n * n % 41)) // _Alonso del Arte_, May 01 2020 %Y A028754 Cf. A010402, A028795. %K A028754 nonn,fini,full,easy %O A028754 1,1 %A A028754 _N. J. A. Sloane_