=(2+1)*1! -(3+1)*2! +(4+1)*3! -(5+1)*4! +(6+1)*5! -(7+1)*6! +(8+1) *7!
= (2! +1!) -(3!+2!) +(4!+3!) -(5!+4!) +(6!+5!) -(7!+6!) +(8!+7!)
= 1 +8!
= 40321