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 A028816 #15 Jul 18 2025 16:52:35
%S A028816 0,1,2,3,11,22,26,101,111,121,202,212,264,307,1001,1111,2002,2285,
%T A028816 2636,10001,10101,10201,11011,11111,11211,20002,20102,22865,24846,
%U A028816 30693,100001,101101,110011,111111,200002,1000001,1001001,1002001,1010101,1011101,1012101
%N A028816 Numbers k such that k^2 is a palindrome with an odd number of digits.
%H A028816 P. De Geest, <a href="https://www.worldofnumbers.com/subsquar.htm">Subsets of Palindromic Squares</a>
%t A028816 id[n_]:=IntegerDigits[n]; palQ[n_]:=FromDigits[Reverse[id[n]]]==n; t={}; Do[If[palQ[x=n^2] && OddQ[Length[id[x]]], AppendTo[t,n]],{n,1012102}]; t (* _Jayanta Basu_, May 13 2013 *)
%t A028816 Join[{0},Select[Range[11 10^5],OddQ[IntegerLength[#^2]]&&PalindromeQ[#^2]&]] (* _Harvey P. Dale_, Jul 18 2025 *)
%Y A028816 Cf. A028817.
%K A028816 nonn,base
%O A028816 1,3
%A A028816 _Patrick De Geest_