n19 1,2,3,4; 0,5,6,7; 0,8,9,10; 0,11,12,13; 0,14,15,16; 1,8,11,14; 1,9,12,15; 1,10,13,16; 2,5,12,16; 2,6,13,17; 2,7,15,18; 3,5,15,17; 3,6,8,18; 3,7,9,14; 4,5,13,18; 4,6,10,11; 4,7,8,17; 9,11,16,18; 10,12,14,17.