0 vertical 1 2 3 4 = 2 * 2 5 6 = 2 * 3 7 8 = 2 * 2 * 2 9 = 3 * 3 10 = 2 * 5 11 12 = 2 * 2 * 3 13 14 = 2 * 7 15 = 3 * 5 16 = 2 * 2 * 2 * 2 17 18 = 2 * 3 * 3 19 20 = 2 * 2 * 5 21 = 3 * 7 22 = 2 * 11 23 24 = 2 * 2 * 2 * 3 25 = 5 * 5