Base 4 Repunits
Table
Format: small prime × proven prime<size> × (probable prime)<size> × [composite]<size> × {unknown}<size>
| 186: | \[{4^{186}-1\over3}\] | 3 × 5 × 7 × 13 × 373 × 5581 × 8681 × 49477 × 384773 × 529510939 × 715827883 × 2147483647 × 2903110321 × 951088215727633<15> × 658812288653553079<18> × 4611545283086450689<19> |