Base 4 Repunits
Table
Format: small prime × proven prime<size> × (probable prime)<size> × [composite]<size> × {unknown}<size>
169: | \[{4^{169}-1\over3}\] | 2731 × 4057 × 8191 × 6740339310641<13> × 4929910764223610387<19> × 18526238646011086732742614043<29> × 3340762283952395329506327023033<31> |