n!!!!! + 1
Table
Format: small prime × proven prime<size> × (probable prime)<size> × [composite]<size> × {unknown}<size>
256: | \[256!!!!!+1\] | 337 × 32533 × 4078225751 × 107665210337779<15> × 5447241670497037139<19> × 4847864070015190430700359<25> × 12986623911191243222837316773<29> |