|
%I #5 Dec 18 2015 18:17:46
%S 1,1,5,65,1349,90013,17612909,7690681987,6760358933241
%N Number of lower triangles of an n X n integer array with all row and column sums zero and all row and column sums of squares <=8
%C Column 2 of A195892
%e Some solutions for n=4
%e ..0........0........0........0........0........0........0........0
%e ..2-2......2-2.....-1.1......2-2.....-2.2......2-2......2-2.....-2.2
%e .-2.2.0...-1.2-1....1-1.0...-2.1.1....0-2.2....0.0.0....0.0.0....0.0.0
%e ..0.0.0.0.-1.0.1.0..0.0.0.0..0.1-1.0..2.0-2.0.-2.2.0.0.-2.2.0.0..2-2.0.0
%K nonn
%O 1,3
%A _R. H. Hardin_ Sep 24 2011
| 