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 A139046 #8 Mar 09 2015 04:29:13 %S A139046 1,2,12,52,1992,43472,8084672,785972800,632010796352,260819509251776, %T A139046 879345967412550400,1508148706710022883840,20993821611583601278837888, %U A139046 147923394778079541856196475392,8426633557858801012990635249817088 %N A139046 Half the number of symmetric n X n binary matrices with the center of gravity of the 1s at the center. %H A139046 R. H. Hardin, Jun 01 2008, <a href="/A139046/b139046.txt">Table of n, a(n) for n = 1..19</a> %Y A139046 Cf. A133413. %K A139046 nonn %O A139046 1,2 %A A139046 _R. H. Hardin_, Jun 01 2008