答案是16吗
n-2)(n-3)(n-4)(n-5)(n-6)/(1-2)/(1-3)/念卜(1-4)/(1-5)/(1-6)×1
+(n-1)(n-3)(n-4)(n-5)(n-6)/(2-1)/仔拦穗(2-3)/衡卜(2-4)/(2-5)/(2-6)×4
+(n-1)(n-2)(n-4)(n-5)(n-6)/(3-1)/(3-2)/(3-4)/(3-5)/(3-6)×16
+(n-1)(n-2)(n-3)(n-5)(n-6)/(4-1)/(4-2)/(4-3)/(4-5)/(4-6)×49
+(n-1)(n-2)(n-3)(n-4)(n-6)/(5-1)/(5-2)/(5-3)/(5-4)/(5-6)×22
+(n-1)(n-2)(n-3)(n-4)(n-5)/(6-1)/(6-2)/(6-3)/(6-4)/(6-5)×M
不会啊