基本的ASCII字符集共有128个字符,其中有96个可打印字符,包括英文大小写字母、数字、标点符号等.
1-20位排列组合有:
C(96,1)=96
C(96,2)=4560
C(96,3)=142880
C(96,4)=3321960
C(96,5)=61124064
C(96,6)=927048304
C(96,7)=11919192480
C(96,8)=132601016340
C(96,9)=1296543270880
C(96,10)=11279926456656
C(96,11)=88188515933856
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C(m,n)=m(m-1)(m-2)(m-3)...(m+1-n)/(1*2*3*4*...*n)(分子、分母各n个连续自然数相乘)