Base 4 Repunits
Table
Format: small prime × proven prime<size> × (probable prime)<size> × [composite]<size> × {unknown}<size>
| 158: | \[{4^{158}-1\over3}\] | 5 × 317 × 2687 × 202029703 × 1113491139767<13> × 381364611866507317969<21> × 201487636602438195784363<24> × 604462909806215075725313<24> |