Base 2 Repunits
Table
Format: small prime × proven prime<size> × (probable prime)<size> × [composite]<size> × {unknown}<size>
| 309: | \[2^{309}-1\] | 7 × 2550183799 × 1953272766780718501831<22> × 3976656429941438590393<22> × 7521737478732572053581227840017636545169<40> |