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 A354597 #13 Jul 09 2022 11:09:48 %S A354597 3,4,5,3,4,4,3,5,4,3,7,5,3,4,7,3,4,4,3,11,4,3,5,9,3,4,5,3,4,4,3,5,4,3, %T A354597 8,7,3,4,7,3,4,4,3,7,4,3,5,5,3,4,7,3,4,4,3,11,4,3,8,7,3,4,5,3,4,4,3,5, %U A354597 4,3,7,5,3,4,8,3,4,4,3,11,4,3,5,9,3,4,5,3,4,4,3,5,4,3,7,9,3,4,7,3 %N A354597 a(n) is the smallest number k>0 such that -n is not a quadratic residue modulo k. %C A354597 All values are prime powers, and every prime power except 2 appears in the sequence. This can be proved using the Chinese remainder theorem. %o A354597 (PARI) a(n) = my(k=2); while (issquare(Mod(-n, k)), k++); k; \\ _Michel Marcus_, Jul 08 2022 %Y A354597 Cf. A139401. %K A354597 nonn %O A354597 1,1 %A A354597 _Bruno Langlois_, Jul 08 2022