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 A027719 #13 Aug 11 2024 14:41:29
%S A027719 0,1,2,10,25,100,1000,1020,1489,2248,10000,10090,100000,100910,102020,
%T A027719 167491,1000000,1000200,1009090,2744934,10000000,10000900,10090910,
%U A027719 24917195,100000000,100909090,103226660,271867456,1000000000,1000002000,1009090910,1577033471
%N A027719 Numbers k such that k^2 + 1 is a palindrome.
%H A027719 Giovanni Resta, <a href="/A027719/b027719.txt">Table of n, a(n) for n = 1..48</a>
%H A027719 P. De Geest, <a href="https://www.worldofnumbers.com/squadd1.htm">Palindromic incremented squares of the form n^2+1</a>
%t A027719 palQ[n_] := Block[{d = IntegerDigits[n]}, d == Reverse[d]]; Select[Range[0, 10^5], palQ[#^2 + 1] &] (* _Giovanni Resta_, Aug 29 2018 *)
%Y A027719 Cf. A002522, A027720, A002778, A070253.
%K A027719 nonn,base
%O A027719 1,3
%A A027719 _Patrick De Geest_
%E A027719 More terms from _Giovanni Resta_, Aug 28 2018