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 A195519 #7 Jul 22 2025 12:44:46 %S A195519 1,1,11,671,401565,2106810049,103074513713971,47878816111749257161 %N A195519 Number of lower triangles of an n X n -5..5 array with all row and column sums zero. %C A195519 Column 5 of A195522 %e A195519 Some solutions for n=4 %e A195519 ..0........0........0........0........0........0........0........0 %e A195519 ..2-2......5-5......4-4......0.0......5-5.....-2.2......0.0.....-5.5 %e A195519 .-4.4.0...-1.3-2...-5.4.1...-1.2-1...-1.3-2....4.0-4...-1.4-3....3-5.2 %e A195519 ..2-2.0.0.-4.2.2.0..1.0-1.0..1-2.1.0.-4.2.2.0.-2-2.4.0..1-4.3.0..2.0-2.0 %K A195519 nonn %O A195519 1,3 %A A195519 _R. H. Hardin_ Sep 20 2011