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 A134011 #22 Dec 12 2023 08:47:25
%S A134011 1,2,3,4,5,4,3,2,1,1,2,3,4,5,4,3,2,1,1,2,3,4,5,4,3,2,1,1,2,3,4,5,4,3,
%T A134011 2,1,1,2,3,4,5,4,3,2,1,1,2,3,4,5,4,3,2,1,1,2,3,4,5,4,3,2,1,1,2,3,4,5,
%U A134011 4,3,2,1,1,2,3,4,5,4,3,2,1,1,2,3,4,5
%N A134011 Period 9: repeat [1, 2, 3, 4, 5, 4, 3, 2, 1].
%H A134011 Vincenzo Librandi, <a href="/A134011/b134011.txt">Table of n, a(n) for n = 0..1000</a>
%H A134011 <a href="/index/Rec#order_09">Index entries for linear recurrences with constant coefficients</a>, signature (0,0,0,0,0,0,0,0,1).
%F A134011 a(n) = a(n-9) for n > 8. G.f.: (1 + x + x^2 + x^3 + x^4)^2/(1 - x^9). - _Chai Wah Wu_, Jun 04 2016
%p A134011 A134011:=n->[1, 2, 3, 4, 5, 4, 3, 2, 1][(n mod 9)+1]: seq(A134011(n), n=0..100); # _Wesley Ivan Hurt_, Jun 11 2016
%t A134011 PadRight[{}, 81, {1,2,3,4,5,4,3,2,1}] (* _Harvey P. Dale_, Oct 31 2011 *)
%o A134011 (Magma) &cat [[1, 2, 3, 4, 5, 4, 3, 2, 1]: n in [0..8]]; // _Wesley Ivan Hurt_, Jun 11 2016
%Y A134011 Cf. A131974.
%K A134011 nonn,easy
%O A134011 0,2
%A A134011 _Paul Curtz_, Jan 10 2008