Base 4 Repunits
Table
Format: small prime × proven prime<size> × (probable prime)<size> × [composite]<size> × {unknown}<size>
| 178: | \[{4^{178}-1\over3}\] | 5 × 179 × 1069 × 62020897 × 18584774046020617<17> × 579017791994999956106149<24> × 123794003928545064364330189<27> × 618970019642690137449562111<27> |