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 A375488 #11 Aug 28 2024 11:27:26 %S A375488 1,2,3,5,7,9,10,11,13,15,17,18,19,23,27,29,31,32,33,35,36,37,41,43,47, %T A375488 53,55,59,61,65,67,71,73,79,83,87,89,91,95,97,98,99,101,103,107,109, %U A375488 112,113,119,127,131,135,136,137,139,143,145,149,151,157,161,163,167,173,179,181,191,193,195,197,199 %N A375488 Numbers k such that k^(sigma(k) - k) == k (mod sigma(k)), where sigma = A000203. %e A375488 9 is in this sequence because 9^(sigma(9) - 9) = 9^(13 - 9) = 9^4 = 6561 modulo 13 is equal to 9. %o A375488 (Magma) [1] cat [k: k in [2..200] | k^(SumOfDivisors(k)-k) mod SumOfDivisors(k) eq k]; %o A375488 (PARI) isok(k) = Mod(k, sigma(k))^(sigma(k) - k) == k; \\ _Michel Marcus_, Aug 18 2024 %Y A375488 Supersequence of A000040. %Y A375488 Cf. A000203, A001065. %K A375488 nonn %O A375488 1,2 %A A375488 _Juri-Stepan Gerasimov_, Aug 17 2024