n!! + 1
Table
Format: small prime × proven prime<size> × (probable prime)<size> × [composite]<size> × {unknown}<size>
156: | \[156!!+1\] | 79 × 149 × 989419525857859<15> × 18952053834381988967<20> × 15506014586842158609476719026349846821305378207124888141817658617635854210817271645630506079895099527<101> |