Base 2 Repunits
Table
Format: small prime × proven prime<size> × (probable prime)<size> × [composite]<size> × {unknown}<size>
| 311: | \[2^{311}-1\] | 5344847 × 2647649373910205158468946067671<31> × 294803681348959296477194164064643062187559537539328375831<57> |