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 A204690 #18 Aug 26 2015 10:12:07
%S A204690 1,1,4,2,1,0,1,3,1,4,0,1,1,3,1,0,1,2,4,4,0,1,4,2,1,0,1,3,1,4,0,1,1,3,
%T A204690 1,0,1,2,4,4,0,1,4,2,1,0,1,3,1,4,0,1,1,3,1,0,1,2,4,4,0,1,4,2,1,0,1,3,
%U A204690 1,4,0,1,1,3,1,0,1,2,4,4,0,1,4,2,1,0,1
%N A204690 n^n (mod 5).
%C A204690 For n>0, periodic with period 20 = A174824(5): repeat [1, 4, 2, 1, 0, 1, 3, 1, 4, 0, 1, 1, 3, 1, 0, 1, 2, 4, 4, 0].
%H A204690 <a href="/index/Rec#order_20">Index entries for linear recurrences with constant coefficients</a>, signature (0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 1).
%t A204690 Table[PowerMod[n,n,5], {n,0,140}]
%t A204690 Join[{1},LinearRecurrence[{0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 1},{1, 4, 2, 1, 0, 1, 3, 1, 4, 0, 1, 1, 3, 1, 0, 1, 2, 4, 4, 0},86]] (* _Ray Chandler_, Aug 26 2015 *)
%Y A204690 Cf. A204689, A174824.
%K A204690 nonn,easy
%O A204690 0,3
%A A204690 _José María Grau Ribas_, Jan 18 2012