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 A066139 #5 Mar 31 2012 13:21:27 %S A066139 0,1,100,121,10000,10201,12100,1000000,1002001,1020100,1022121, %T A066139 1210000,1212201,100000000,100020001,100200100,100220121,102010000, %U A066139 102212100,121000000,121022001,121220100,10000000000,10000200001,10002000100 %N A066139 Squares in every base >=3 (involving no carries and no digit apart from 0, 1 and 2). %C A066139 The reverse of every element in the list is also in the list. %C A066139 Concatenated coefficients of polynomial squares where all coefficients in the square are 0, 1, or 2. - _Franklin T. Adams-Watters_, Mar 12 2006 %e A066139 10100^2 = 102010000 is in the list but 10101^2 = 102030201 (if working in bases >=4) or = 102100201 (if working in base 3) is not. %K A066139 base,nonn %O A066139 0,3 %A A066139 _Henry Bottomley_, Dec 07 2001