Base 4 Repunits
Table
Format: small prime × proven prime<size> × (probable prime)<size> × [composite]<size> × {unknown}<size>
| 238: | \[{4^{238}-1\over3}\] | 5 × 29 × 43 × 113 × 127 × 137 × 239 × 953 × 2381 × 9521 × 20231 × 26317 × 42841 × 43691 × 131071 × 823481 × 823679683 × 62983048367<11> × 131105292137<12> × 536296539263941<15> × 143162553165560959297<21> × 18292898984156916156396101<26> |