Base 2 Repunits
Table
Format: small prime × proven prime<size> × (probable prime)<size> × [composite]<size> × {unknown}<size>
| 305: | \[2^{305}-1\] | 31 × 1831 × 2441 × 4271 × 270841 × 484074637694471<15> × 2305843009213693951<19> × 364371848053973128400380293624417256758401<42> |