1 * 8 + 1 = 9 12 * 8 + 2 = 98 123 * 8 + 3 = 987 1234 * 8 + 4 = 9876 12345 * 8 + 5 = 98765 123456 * 8 + 6 = 987654 1234567 * 8 + 7 = 9876543 12345678 * 8 + 8 = 98765432 123456789 * 8 + 9 = 987654321 2136279841 - 1