Base 4 Repunits
Table
Format: small prime × proven prime<size> × (probable prime)<size> × [composite]<size> × {unknown}<size>
| 213: | \[{4^{213}-1\over3}\] | 3 × 7 × 5113 × 17467 × 66457 × 102241 × 228479 × 48544121 × 56409643 × 212885833 × 13952598148481<14> × 2849881972114740679<19> × 4205268574191396793<19> × 203525545766301306933226271929<30> |