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 A139680 #8 May 08 2020 18:22:18 %S A139680 1,2,8,64,1024,28217,1146419,62951431,4451407563,392447922178, %T A139680 42102440864054,5391561047209898,811314950514676762, %U A139680 141599096294933832181,28348376853054890615951,6448749608634353498219753,1653216120840296892595307251,474197636984335589673286631814 %N A139680 Number of n X n symmetric binary matrices with no row sum greater than 4. %H A139680 Andrew Howroyd, <a href="/A139680/b139680.txt">Table of n, a(n) for n = 0..40</a> %Y A139680 Column k=4 of A334548. %K A139680 nonn %O A139680 0,2 %A A139680 _R. H. Hardin_, Jun 13 2008 %E A139680 Terms a(13) and beyond from _Andrew Howroyd_, May 08 2020