A double factorial prime is a prime number of the form 
,
where 
is a nonnegative integer and 
is a double factorial.
is prime for 
, 4, 6, 8, 16, 26, 64, 82, 90, 118, 194, 214, 728, ... (OEIS
A007749). The following table summarizes the
largest examples reported through 2016.
 | digits | discoverer |
 | 169,435 | S. Fukui (Jun. 5, 2015) |
 | 229,924 | S. Fukui (Jun. 5, 2015) |
 | 344,538 | S. Fukui (Apr. 21, 2016) |
is prime for 
, 1, 2, 518, 33416, 37310, 52608, 123998, 220502, ... (OEIS
A080778). The following table summarizes the
largest examples reported through 2017.
 | digits | discoverer |
 | 112,762 | H. Jamke (Jan. 3, 2008) |
 | 288,864 | S. Fukui (Jun. 5, 2015) |
 | 541,239 | S. Fukui (Jan. 17, 2017) |
."