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 A263607 #9 Oct 24 2015 12:44:27 %S A263607 0,1,2,11,101,102,202,211,1001,1021,2002,10001,10022,11012,12201, %T A263607 20002,100001,100201,200002,201102,1000001,1000222,1002201,1011221, %U A263607 1101211,1211201,1212022,2000002,10000001,10002001,10200102,10201121,11011211,12212101,20000002,20011002,100000001,100002222,100022001 %N A263607 Base 3 numbers whose square is a palindrome in base 3. %H A263607 Chai Wah Wu, <a href="/A263607/b263607.txt">Table of n, a(n) for n = 1..288</a> %H A263607 G. J. Simmons, <a href="/A002778/a002778.pdf">On palindromic squares of non-palindromic numbers</a>, J. Rec. Math., 5 (No. 1, 1972), 11-19. [Annotated scanned copy] %Y A263607 Cf. A002778, A029984, A263608, A029985. %K A263607 nonn,base %O A263607 1,3 %A A263607 _N. J. A. Sloane_, Oct 22 2015