A195520 - OEIS

%I #5 Dec 18 2015 18:17:46

%S 1,1,13,1105,1089411,11131321791,1252997799222737,

%T 1582560262323178069903

%N Number of lower triangles of an n X n -6..6 array with all row and column sums zero

%C Column 6 of A195522

%e Some solutions for n=4

%e ..0........0........0........0........0........0........0........0

%e ..0.0......0.0......0.0.....-3.3.....-5.5.....-2.2......5-5.....-5.5

%e ..4.0-4...-4.4.0....3-2-1...-3.3.0...-1-3.4....4.0-4...-6.4.2....3-4.1

%e .-4.0.4.0..4-4.0.0.-3.2.1.0..6-6.0.0..6-2-4.0.-2-2.4.0..1.1-2.0..2-1-1.0

%K nonn

%O 1,3

%A _R. H. Hardin_ Sep 20 2011