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 A213796 #8 Apr 08 2020 01:56:43 %S A213796 1,1,5,57,3249,815263,932587453,4893373431575,119570350092328225, %T A213796 13715276642286471266345,7439775168632414842497242951, %U A213796 19190656372074846793620422063221831,236483103820478991417179706813598595965425 %N A213796 Number of n X n 0..4 symmetric arrays with every row summing to 2*n. %e A213796 Some solutions for n=4 %e A213796 ..3..1..1..3....1..3..4..0....4..0..4..0....2..4..0..2....0..1..4..3 %e A213796 ..1..4..1..2....3..3..1..1....0..1..3..4....4..2..2..0....1..3..1..3 %e A213796 ..1..1..3..3....4..1..0..3....4..3..0..1....0..2..3..3....4..1..2..1 %e A213796 ..3..2..3..0....0..1..3..4....0..4..1..3....2..0..3..3....3..3..1..1 %Y A213796 Column 4 of A213800. %K A213796 nonn %O A213796 0,3 %A A213796 _R. H. Hardin_, Jun 20 2012 %E A213796 a(0)=1 prepended and a(8)-a(12) from _Andrew Howroyd_, Apr 07 2020