Base 4 Repunits
Table
Format: small prime × proven prime<size> × (probable prime)<size> × [composite]<size> × {unknown}<size>
| 278: | \[{4^{278}-1\over3}\] | 5 × 557 × 1408349 × 4506937 × 15736774913<11> × 492717674609<12> × 5625767248687<13> × 12763660054721<14> × 123876132205208335762278423601<30> × 51542639524661795300074174250365699<35> × 1251163891299967635860272509229764287909<40> |