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 A131669 #16 Jan 01 2024 23:49:38
%S A131669 1,3,5,7,9,2,4,6,8,1,3,5,7,9,2,4,6,8,1,3,5,7,9,2,4,6,8,1,3,5,7,9,2,4,
%T A131669 6,8,1,3,5,7,9,2,4,6,8,1,3,5,7,9,2,4,6,8,1,3,5,7,9,2,4,6,8,1,3,5,7,9,
%U A131669 2,4,6,8,1,3,5,7,9,2,4,6,8
%N A131669 Odd digits followed by positive even digits.
%H A131669 <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).
%t A131669 PadRight[{},120,{1,3,5,7,9,2,4,6,8}] (* _Harvey P. Dale_, Jan 17 2015 *)
%K A131669 nonn,base,easy
%O A131669 1,2
%A A131669 _Paul Curtz_, Oct 03 2007