Base 4 Repunits
Table
Format: small prime × proven prime<size> × (probable prime)<size> × [composite]<size> × {unknown}<size>
| 321: | \[{4^{321}-1\over3}\] | 3 × 7 × 643 × 154723 × 20636399209<11> × 17866285599391<14> × 480625710015394052365153<24> × 5718761969788697451457489<25> × 84115747449047881488635567801<29> × 162259276829213363391578010288127<33> × 210516800089955301807292488792588188869650399862249<51> |