Base 4 Repunits
Table
Format: small prime × proven prime<size> × (probable prime)<size> × [composite]<size> × {unknown}<size>
| 171: | \[{4^{171}-1\over3}\] | 32 × 7 × 192 × 73 × 571 × 32377 × 174763 × 524287 × 1212847 × 93507247 × 160465489 × 3042645634792541312037847<25> × 19177458387940268116349766612211<32> |