18
18 = 2 * 3 * 3
218 - 1 = 3 * 3 * 3 * 7 * 19 * 73
1018 - 1 = 3 * 3 * 3 * 3 * 7 * 11 * 13 * 19 * 37 * 52579 * 333667
17 - 18 - 19
0 - 1 - 2 - 3 - 4 - 5 - 6 - 7 - 8 - 9
Mathematics Encyclopedia
Hellenica World - Scientific Library
