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 A025683 #9 Jul 06 2025 09:02:22
%S A025683 0,1,0,2,1,0,3,2,1,0,4,3,2,1,0,5,4,3,2,1,0,6,5,4,3,2,1,0,7,6,5,4,3,2,
%T A025683 1,0,8,7,6,5,4,3,2,1,0,9,8,7,6,5,4,3,2,1,0,10,9,8,7,6,5,4,3,2,1,0,11,
%U A025683 10,9,8,7,6,5,4,3,2,1,0,12,11,10,9,8,7,6,5,4,3,2,1,0,13,12,11,10,9,8,7,6,5,4,3
%N A025683 Exponent of 9 (value of i) in n-th number of form 9^i*10^j.
%t A025683 Table[Range[n,0,-1],{n,0,15}]//Flatten (* _Harvey P. Dale_, Jan 20 2022 *)
%Y A025683 Cf. A025653. Differs from A025581 at a(253).
%K A025683 nonn
%O A025683 1,4
%A A025683 _David W. Wilson_