Base 18 Repunits
Table
Format: small prime × proven prime<size> × (probable prime)<size> × [composite]<size> × {unknown}<size>
57: | \[{18^{57}-1\over17}\] | 73 × 6841 × 1288363483639<13> × 6089884909802812423<19> × 1135070056132121343004681823047441<34> |