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 A386872 #11 Aug 19 2025 18:02:27 %S A386872 1,2,6,12,18,24,54,48,72,96,270,120,450,384,288,240,2310,360,1890,480, %T A386872 1152,3150,4050,720,2592,6930,1800,1920,17010,1440 %N A386872 Smallest k for which A385662(k) = n, or -1 if no such k exists. %o A386872 (PARI) f(n) = sumdiv(n, d, Mod(d, n)^d == Mod(-d, n)^d); \\ A385662 %o A386872 a(n) = my(k=1); while (f(k) != n, k++); k; \\ _Michel Marcus_, Aug 06 2025 %Y A386872 Cf. A385729, A385731, A386410, A385318, A385662. %K A386872 nonn,more,new %O A386872 1,2 %A A386872 _Juri-Stepan Gerasimov_, Aug 06 2025