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 A215256 #12 Jun 29 2014 03:02:21 %S A215256 1,1,1,11,11,101,11,111,111,1001,101,101,11,101,111,1111,1111,10001, %T A215256 1001,1001,101,10101,1001,111,111,1001,101,11011,111,111,1111,11111, %U A215256 11111,100001,10001,10001,11011,1001,1001,1001,101,1001,10101,10101,1001,101101 %N A215256 Longest palindromic factor of (n base 2); in case of tie choose largest; if it begins with 0 complement it. %C A215256 The "if it begins with 0 complement it" clause is required because nonzero terms in the OEIS may not begin with 0. %H A215256 Lars Blomberg, <a href="/A215256/b215256.txt">Table of n, a(n) for n = 0..9999</a> %e A215256 n=10 = 1010, longest palindromic factor is 101. %e A215256 n=12 = 1100, there are two palindromic factors of length 2, namely 11 and 00, and we choose the larger, 11. %e A215256 n=24 = 11000, longest palindromic factor is 000, complementing gives 111. %Y A215256 Cf. A050430, A215467. %K A215256 nonn,base %O A215256 0,4 %A A215256 _N. J. A. Sloane_, Aug 15 2012 %E A215256 More terms from _Lars Blomberg_, Jun 29 2014