Base 4 Repunits
Table
Format: small prime × proven prime<size> × (probable prime)<size> × [composite]<size> × {unknown}<size>
| 197: | \[{4^{197}-1\over3}\] | 7487 × 197002597249<12> × 1348959352853811313<19> × 251951573867253012259144010843<30> × 26828803997912886929710867041891989490486893845712448833<56> |