推 qbay :感謝，我找到盲點了XD 10/24 23:43
※ 引述《qbay (Q貝)》之銘言：
: 想請教一題跟高斯符號有關問題
: [n/1!]+[n/2!]+[n/3!]+[n/4!]+[n/5!]+[n/6!]+[n/7!]+[n/8!]=685
: 請問最小的正整數n為多少？
: 今天一個學生拿這題過來問我，瞬間我傻掉了＝ ＝
: 想知道這要怎麼處理，謝謝
n = [n/1!] <= 685, since 5! = 120, 6!=720,...
so [n/6!] = [n/7!] = [n/8!] = 0
so [n/1!]+[n/2!]+[n/3!]+[n/4!]+[n/5!] = 685
685 <= n/1! + n/2! + n/3! + n/4! + n/5! < 690
685 <= 205n/120 < 690
解出來，在驗證一下就好了
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