Base 18 Repunits
Table
Format: small prime × proven prime<size> × (probable prime)<size> × [composite]<size> × {unknown}<size>
81: | \[{18^{81}-1\over17}\] | 73 × 487 × 991 × 23761 × 34327 × 253369 × 1464049 × 4464073 × 27470503 × 1964508729666289645801020967<28> × 2317745463335260122632425120711<31> |