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 A168541 #18 Jul 03 2020 18:41:42
%S A168541 2,5,20,50,200,202,220,500,505,550,2000,2002,2020,2022,2200,2202,2220,
%T A168541 5000,5005,5050,5055,5500,5505,5550,20000,20002,20020,20022,20200,
%U A168541 20202,20220,20222,22000,22002,22020,22022,22200,22202,22220,50000,50005
%N A168541 Numbers consisting of either 2's and 0's or 5's and 0's.
%C A168541 A subset of the divisors of zero in carryless arithmetic mod 10, e.g., 5 * 44 = 0.
%H A168541 David Applegate, Marc LeBrun and N. J. A. Sloane, <a href="http://neilsloane.com/doc/carry1.pdf">Carryless Arithmetic (I): The Mod 10 Version</a>.
%H A168541 <a href="/index/Ar#10-automatic">Index entries for 10-automatic sequences</a>.
%H A168541 <a href="/index/Ca#CARRYLESS">Index entries for sequences related to carryless arithmetic</a>
%t A168541 lst = {2, 5}; k = 1; While[k < 10^5, id = Union@ IntegerDigits@k; len = Length@ id; If[ len == 2 && id == {0, 2} || id == {0, 5}, AppendTo[lst, k]]; k++ ]; lst (* _Robert G. Wilson v_, Jul 12 2010 *)
%t A168541 Join[{2,5},Sort[Flatten[Table[Select[FromDigits/@Tuples[{k,0},6],DigitCount[ #,10,0]>0 && DigitCount[#,10,k]>0&],{k,{2,5}}]]]] (* _Harvey P. Dale_, Jul 03 2020 *)
%Y A168541 Cf. A004520, A059729, A168294, A169884.
%K A168541 nonn,base,easy
%O A168541 1,1
%A A168541 _David Applegate_, _Marc LeBrun_ and _N. J. A. Sloane_, Jul 06 2010
%E A168541 More terms from _Robert G. Wilson v_, Jul 12 2010