Base 4 Repunits
Table
Format: small prime × proven prime<size> × (probable prime)<size> × [composite]<size> × {unknown}<size>
| 254: | \[{4^{254}-1\over3}\] | 5 × 509 × 18797 × 26417 × 72118729 × 140385293 × 2792688414613<13> × 8988357880501<13> × 90133566917913517709497<23> × 56713727820156410577229101238628035243<38> × 170141183460469231731687303715884105727<39> |