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 A139788 #26 Feb 27 2024 03:05:20
%S A139788 1,7,3,9,5,1,7,3,9,5,1,7,3,9,5,1,7,3,9,5,1,7,3,9,5,1,7,3,9,5,1,7,3,9,
%T A139788 5,1,7,3,9,5,1,7,3,9,5,1,7,3,9,5,1,7,3,9,5,1,7,3,9,5,1,7,3,9,5,1,7,3,
%U A139788 9,5,1,7,3,9,5,1,7,3,9,5
%N A139788 Period 5: repeat [1, 7, 3, 9, 5].
%H A139788 <a href="/index/Rec#order_05">Index entries for linear recurrences with constant coefficients</a>, signature (0,0,0,0,1).
%F A139788 a(n) = (1-4n) mod 10. - _Wesley Ivan Hurt_, Dec 03 2022
%t A139788 PadRight[{},100,{1,7,3,9,5}] (* _Harvey P. Dale_, Aug 14 2023 *)
%o A139788 (PARI) a(n)=[1,7,3,9,5][n%5+1] \\ _Charles R Greathouse IV_, Jun 02 2011
%K A139788 nonn,easy,less
%O A139788 0,2
%A A139788 _Paul Curtz_, May 21 2008