Base 4 Repunits
Table
Format: small prime × proven prime<size> × (probable prime)<size> × [composite]<size> × {unknown}<size>
| 214: | \[{4^{214}-1\over3}\] | 5 × 643 × 857 × 843589 × 8174912477117<13> × 23528569104401<14> × 37866809061660057264219253397<29> × 84115747449047881488635567801<29> × 162259276829213363391578010288127<33> |