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 A056525 #20 Aug 21 2020 14:19:25
%S A056525 1,2,3,4,5,6,7,8,9,101,111,121,131,141,151,161,171,181,191,202,212,
%T A056525 222,232,242,252,262,272,282,292,303,313,323,333,343,353,363,373,383,
%U A056525 393,404,414,424,434,444,454,464,474,484,494,505,515,525,535,545,555,565
%N A056525 Palindromes with odd number of digits.
%C A056525 Concatenation of all but final digits of n with reverse of n (keeping leading zeros in the reverse)
%C A056525 A178788(a(n)) = 0 for n > 9. [From _Reinhard Zumkeller_, Jun 30 2010]
%H A056525 Reinhard Zumkeller, <a href="/A056525/b056525.txt">Table of n, a(n) for n = 1..10000</a>
%H A056525 <a href="/index/Fi#final">Index entries for sequences related to final digits of numbers</a>
%F A056525 a(n) = floor[n/10]*10^A055642(n)+A004086(n)
%t A056525 Join[Range[9],Table[FromDigits[Join[x=IntegerDigits[n],Reverse[Drop[x,-1]]]],{n,10,56}]] (* _Jayanta Basu_, May 29 2013 *)
%t A056525 Select[Flatten[Table[Range[10^n,10^(n+1)-1],{n,0,2,2}]],PalindromeQ] (* Requires Mathematica version 10 or later *) (* _Harvey P. Dale_, Aug 21 2020 *)
%o A056525 (Haskell)
%o A056525 a056525 n = a056525_list !! (n-1)
%o A056525 a056525_list = [1..9] ++ [read (ns ++ [z] ++ reverse ns) |
%o A056525 n <- [1..], let ns = show n, z <- "0123456789"]
%o A056525 -- _Reinhard Zumkeller_, Dec 28 2011
%Y A056525 Cf. A002113, A004086, A056524.
%K A056525 base,easy,nonn
%O A056525 1,2
%A A056525 _Henry Bottomley_, Jun 16 2000