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 A175921 #18 Oct 13 2022 14:21:22
%S A175921 1,2,2,-1,1,1,2,2,-1,1,1,2,2,-1,1,1,2,2,-1,1,1,2,2,-1,1,1,2,2,-1,1,1,
%T A175921 2,2,-1,1,1,2,2,-1,1,1,2,2,-1,1,1,2,2,-1,1,1,2,2,-1,1,1,2,2,-1,1,1,2,
%U A175921 2,-1,1,1,2,2,-1,1,1,2,2,-1,1
%N A175921 Period 5: repeat [1, 2, 2, -1, 1].
%H A175921 <a href="/index/Rec#order_05">Index entries for linear recurrences with constant coefficients</a>, signature (0,0,0,0,1).
%t A175921 PadRight[{},120,{1,2,2,-1,1}] (* _Harvey P. Dale_, Dec 30 2016 *)
%o A175921 (PARI) a(n)=[1,1,2,2,-1][n%5+1] \\ _Charles R Greathouse IV_, Mar 12 2017
%Y A175921 Cf. A040001, A028356, A142150, A000012, A175922.
%K A175921 sign,easy,less
%O A175921 1,2
%A A175921 _Jaroslav Krizek_, Oct 17 2010
%E A175921 Edited by _Joerg Arndt_, Sep 16 2013