Base 4 Repunits
Table
Format: small prime × proven prime<size> × (probable prime)<size> × [composite]<size> × {unknown}<size>
| 353: | \[{4^{353}-1\over3}\] | 931921 × 2927455476800301964116805545194017<34> × 3803909572078746837295094051706948091<37> × 6725414756111955781503880188940925566051960039574573675843402666863<67> × 1607818533384485707707842837146335251451162017762519557029955613946641<70> |