Base 4 Repunits
Table
Format: small prime × proven prime<size> × (probable prime)<size> × [composite]<size> × {unknown}<size>
215: | \[{4^{215}-1\over3}\] | 11 × 31 × 431 × 1721 × 9719 × 2099863 × 9084611 × 731516431 × 514851898711<12> × 2932031007403<13> × 297927289744047764444862191<27> × 59904608378705661377430182608711698924130721<44> |