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 A181476 #7 Feb 09 2021 01:57:50
%S A181476 1,2,8,9,36,128,576,625,900,1156,2304,2601,5185,6561,10082,10404,
%T A181476 27225,32768,57600,117649,181476,260100,285156,367236,378225,443521,
%U A181476 607825,617796,645248,656100,665856,783225,1115136,1394450,1500625,1782225
%N A181476 Numbers k such that k^k == 1 (mod sigma(k)).
%C A181476 If p is prime then p^m is in the sequence iff m is of the form p^t-1 where t is a nonnegative integer.
%t A181476 Join[{1}, Select[Range[1800000], PowerMod[ #,#,DivisorSigma[1,# ]]==1 &]]
%o A181476 (PARI) isok(k) = Mod(k, sigma(k))^k == 1; \\ _Michel Marcus_, Feb 09 2021
%Y A181476 Cf. A000203, A177006.
%K A181476 nonn
%O A181476 1,2
%A A181476 _Farideh Firoozbakht_, May 23 2010