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 A139810 #6 Mar 31 2012 12:35:07 %S A139810 1,2,15,417,42176,15701273,21418970801,107224417436160, %T A139810 1968910887183791359,132633131268024896655873, %U A139810 32775983842712963307230834176,29712661745725058784174163778464369 %N A139810 Number of n X n binary matrices containing no 2 X 2 all-1s sub-block. %H A139810 R. H. Hardin, <a href="/A139810/b139810.txt">Table of n, a(n) for n = 0..19</a> %K A139810 nonn %O A139810 0,2 %A A139810 _R. H. Hardin_, May 23 2008