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 A213794 #9 Apr 08 2020 01:57:09 %S A213794 1,1,3,13,169,5673,526443,133721189,95133854529,190409704025737, %T A213794 1081810465812816481,17533275809917986947451, %U A213794 814583187343481957681992873,108889213625061640897043875544377,42017261328544343771207789776696995237,46930798910194830781686389018692804741926963 %N A213794 Number of n X n 0..2 symmetric arrays with every row summing to n. %e A213794 Some solutions for n=4 %e A213794 ..0..2..2..0....2..2..0..0....2..1..0..1....1..1..0..2....1..2..0..1 %e A213794 ..2..0..0..2....2..1..1..0....1..1..2..0....1..2..1..0....2..1..0..1 %e A213794 ..2..0..1..1....0..1..1..2....0..2..1..1....0..1..1..2....0..0..2..2 %e A213794 ..0..2..1..1....0..0..2..2....1..0..1..2....2..0..2..0....1..1..2..0 %Y A213794 Column 2 of A213800. %K A213794 nonn %O A213794 0,3 %A A213794 _R. H. Hardin_, Jun 20 2012 %E A213794 a(0)=1 prepended and terms a(10) and beyond from _Andrew Howroyd_, Apr 07 2020