81393657020domain: NAppears in sequencesAlternating factorials: 0! - 1! + 2! - ... + (-1)^n n!at n=14A058006a(0) = 0, a(1) = 1, and for n >= 2, a(n) = (n-1) * a(n-2) + (n-2) * a(n-1).at n=15A153229