Base 4 Repunits
Table
Format: small prime × proven prime<size> × (probable prime)<size> × [composite]<size> × {unknown}<size>
| 115: | \[{4^{115}-1\over3}\] | 11 × 31 × 47 × 691 × 14951 × 178481 × 2796203 × 4036961 × 1884103651 × 345767385170491<15> × 2646507710984041<16> |