First of all, to find the quotient m and the remainder n of n divided by 3, there are three situations:

n = 1，x - 1 = o

n=2，xx - 1 = oo

n=3，xxx - 2 = ooo+xxx

n=4，xxxx-3 = 0xx+xxxo+oooo

n=5，xxxxx-4 = xxxoo+oxxxo+ooxxx+oooo

The remainder n is 0:

1+A(m- 1，m)+A(m-2，m)+......+A(0，m)= 1+(m- 1)！ +(m-2)！ +0!

The remainder n is 1:

The remainder n is 2: