Base 18 Repunits
Table
Format: small prime × proven prime<size> × (probable prime)<size> × [composite]<size> × {unknown}<size>
| 68: | \[{18^{68}-1\over17}\] | 52 × 13 × 17 × 19 × 137 × 443 × 1429 × 6257 × 20786377 × 1292838509 × 1895634885375961<16> × 61187167524277573<17> × 7563707819165039903<19> |