Base 4 Repunits
Table
Format: small prime × proven prime<size> × (probable prime)<size> × [composite]<size> × {unknown}<size>
| 136: | \[{4^{136}-1\over3}\] | 5 × 172 × 137 × 257 × 953 × 26317 × 43691 × 131071 × 354689 × 383521 × 2368179743873<13> × 2879347902817<13> × 373200722470799764577<21> |