Base 4 Repunits
Table
Format: small prime × proven prime<size> × (probable prime)<size> × [composite]<size> × {unknown}<size>
| 172: | \[{4^{172}-1\over3}\] | 5 × 17 × 173 × 431 × 9719 × 101653 × 500177 × 2099863 × 3855260977 × 1759217765581<13> × 2932031007403<13> × 64082150767423457<17> × 1425343275103126327372769<25> |