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 A166121 #13 Aug 23 2023 18:27:34
%S A166121 791621579,776537851,19300779,776488094,422669176,388384265,50381743,
%T A166121 17604196,388337603,34424740,824599,791621579,776537851,19300779,
%U A166121 776488094,422669176,388384265,50381743,17604196,388337603,34424740
%N A166121 Let dsf(n) = n_1^{n_1}+n_2^{n_2}+n_3^{n_3} + n_m^{n_m}, where {n_1,n_2,n_3,...n_m} is the list of the digits of an integer n. dsf(791621579) = 776537851 and dsf(776537851) = 19300779, ..., dsf(824599) = 791621579, ... in this way these 11 numbers make a loop for the function dsf.
%C A166121 In fact there are only 8 loops among all the nonnegative integers for the "dsf" function that we defined. We have discovered this fact through calculations using Mathematica and general-purpose languages.
%H A166121 Ryohei Miyadera, <a href="http://library.wolfram.com/infocenter/MathSource/5686/">Curious Properties of an Iterative Process</a>,Mathsource, Wolfram Library Archive.
%H A166121 Shoei Takahashi, Unchone Lee, Hikaru Manabe, Aoi Murakami, Daisuke Minematsu, Kou Omori, and Ryohei Miyadera, <a href="https://arxiv.org/abs/2308.06691">Curious Properties of Iterative Sequences</a>, arXiv:2308.06691 [math.GM], 2023.
%F A166121 Let dsf(n) = n_1^{n_1}+n_2^{n_2}+n_3^{n_3} + n_m^{n_m}, where {n_1,n_2,n_3,...n_m} is the list of the digits of an integer n. By applying the function dsf to 791621579 we can get a loop of length 11.
%e A166121 This is an reiterative process that starts with 791621579.
%t A166121 dsf[n_] := Block[{m = n, t}, t = IntegerDigits[m]; Sum[Max[1, t[[k]]]^t[[k]], {k, Length[t]}]]; NestList[dsf,791621579,22]
%Y A166121 Cf. A165942, A166024, A166072.
%K A166121 base,nonn
%O A166121 1,1
%A A166121 _Ryohei Miyadera_, Takuma Nakaoka and Koichiro Nishimura, Oct 07 2009