Base 4 Repunits
Table
Format: small prime × proven prime<size> × (probable prime)<size> × [composite]<size> × {unknown}<size>
| 247: | \[{4^{247}-1\over3}\] | 2731 × 8191 × 15809 × 174763 × 207481 × 524287 × 10049443 × 355011619 × 6459570124697<13> × 402004106269663<15> × 1282816117617265060453496956212169<34> × 213379941663827592701819558102368170760508803<45> |