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 A195517 #7 Jul 22 2025 12:44:32 %S A195517 1,1,7,175,27267,23663523,122092290831,3806404472713603, %T A195517 731708552185212577507 %N A195517 Number of lower triangles of an n X n -3..3 array with all row and column sums zero. %C A195517 Column 3 of A195522 %e A195517 Some solutions for n=4 %e A195517 ..0........0........0........0........0........0........0........0 %e A195517 .-1.1......0.0......2-2......0.0.....-3.3.....-2.2.....-2.2......2-2 %e A195517 .-2-1.3....2-2.0....1.0-1....3.0-3....3-3.0....0-3.3....0-3.3....0.1-1 %e A195517 ..3.0-3.0.-2.2.0.0.-3.2.1.0.-3.0.3.0..0.0.0.0..2.1-3.0..2.1-3.0.-2.1.1.0 %K A195517 nonn %O A195517 1,3 %A A195517 _R. H. Hardin_ Sep 20 2011