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 A104459 #23 Apr 17 2025 17:21:15
%S A104459 1,2,10,11,100,110,1000,1100,10000,11000,100000,110000,1000000,
%T A104459 1100000,10000000,11000000,100000000,110000000,1000000000,1100000000,
%U A104459 10000000000,11000000000,100000000000,110000000000,1000000000000,1100000000000,10000000000000
%N A104459 Possible differences between adjacent palindromes.
%C A104459 Possible first differences of A002113.
%H A104459 <a href="/index/Rec#order_02">Index entries for linear recurrences with constant coefficients</a>, signature (0,10).
%F A104459 a(n) = 2 if n = 2; 11*10^((n-4)/2) if n even >= 4; 10^((n-1)/2) if n odd.
%F A104459 a(n) = 10*a(n-2), starting 1,2,10,11.
%F A104459 G.f.: x*(1 + 2*x - 9*x^3)/(1 - 10*x^2). - _Stefano Spezia_, Dec 08 2021
%e A104459 536635 and 537735 are adjacent palindromes, so 537735-536635 = 1100 is in the sequence.
%t A104459 PalindromeQ[n_]:=Reverse[IntegerDigits[n]]==IntegerDigits[n];q=0;lst={};Do[If[PalindromeQ[n],AppendTo[lst,n-q];q=n],{n,10!}];Union@lst (* _Vladimir Joseph Stephan Orlovsky_, Oct 26 2009 *)
%t A104459 Flatten[Join[{1,2},Table[{10,11}10^n,{n,0,15}]]] (* _Harvey P. Dale_, Dec 22 2012 *)
%Y A104459 Cf. A002113, A109868.
%K A104459 base,easy,nonn
%O A104459 1,2
%A A104459 _David W. Wilson_, Mar 08 2005