Base 4 Repunits
Table
Format: small prime × proven prime<size> × (probable prime)<size> × [composite]<size> × {unknown}<size>
| 157: | \[{4^{157}-1\over3}\] | 15073 × 2350291 × 852133201 × 60726444167<11> × 1654058017289<13> × 2134387368610417<16> × 17751783757817897<17> × 96833299198971305921<20> |