Base 4 Repunits
Table
Format: small prime × proven prime<size> × (probable prime)<size> × [composite]<size> × {unknown}<size>
| 209: | \[{4^{209}-1\over3}\] | 23 × 89 × 419 × 683 × 174763 × 524287 × 94803416684681<14> × 1512348937147247<16> × 3410623284654639440707<22> × 5346950541323960232319657<25> × 1607792018780394024095514317003<31> |