0 vertical 1 ref1 2 ref2 3 ref3 4 = 2 * 2 ref4 5 ref5 6 = 2 * 3 ref6 7 ref7 8 = 2 * 2 * 2 ref8 9 = 3 * 3 ref9 10 = 2 * 5 ref10 11 ref11 12 = 2 * 2 * 3 ref12 13 ref13 14 = 2 * 7 ref14 15 = 3 * 5 ref15 16 = 2 * 2 * 2 * 2 ref16 17 ref17 18 = 2 * 3 * 3 ref18 19 ref19 20 = 2 * 2 * 5 ref20 21 = 3 * 7 ref21 22 = 2 * 11 ref22 23 ref23 24 = 2 * 2 * 2 * 3 ref24 25 = 5 * 5 ref25