Base 3 Repunits
Table
Format: small prime × proven prime<size> × (probable prime)<size> × [composite]<size> × {unknown}<size>
| 221: | \[{3^{221}-1\over2}\] | 443 × 1871 × 34511 × 797161 × 60923689584342791398642907184808386306560206807547243570697195224906504237067588551869427<89> |