Base 3 Repunits
Table
Format: small prime × proven prime<size> × (probable prime)<size> × [composite]<size> × {unknown}<size>
| 197: | \[{3^{197}-1\over2}\] | 9851 × 741019334164502879<18> × 11472574961994477441469621<26> × 58733573000937067164211172290216978734891718609<47> |