Base 4 Repunits
Table
Format: small prime × proven prime<size> × (probable prime)<size> × [composite]<size> × {unknown}<size>
| 187: | \[{4^{187}-1\over3}\] | 23 × 89 × 683 × 43691 × 131071 × 707983 × 1032670816743843860998850056278950666491537<43> × 2191165825376888084750157716424579062015865776131<49> |