I want to calculate 12.1!!!!!! , Just for curiosity. (One of my friend texted the term to me for some complex reason.)
I searched for multifactorial in terms of gamma function or equation, and found nothing if factorial goes more than double. I know the answer is somewhere between 12*6 and 13*7*1, but can I be more accurate than linearly interpolating those values?
(By the way, I spend an hour to learn thatt 12.1!!≠(12.1!)!. I wonder how huge the answer will be if it was 6 repetitive factorial, but not for now.)