n!!!! + 1
Table
Format: small prime × proven prime<size> × (probable prime)<size> × [composite]<size> × {unknown}<size>
255: | \[255!!!!+1\] | 2 × 1048918357 × 290150575217<12> × 273544013766931<15> × 2016243521389066127<19> × 84592724475366796877806035037<29> × 438019941516878535334943404298513341797042533<45> |