61154044domain: NAppears in sequences6X6X6 triangular graph without horizontal edges coloring a rectangular array: number of nX2 0..20 arrays where 0..20 label nodes of a graph with edges 0,1 0,2 1,3 1,4 2,4 2,5 3,6 3,7 4,7 4,8 5,8 5,9 6,10 6,11 7,11 7,12 8,12 8,13 9,13 9,14 10,15 10,16 11,16 11,17 12,17 12,18 13,18 13,19 14,19 14,20 and every array movement to a horizontal or vertical neighbor moves along an edge of this graph.at n=7A223461