回復 1# niklacage 的帖子
6.
f(25) = f(f(32)) = f(26) = 20
f(24) = f(f(31)) = f(25) = 20
f(23) = f(f(30)) = f(24) = 20
:
:
每一項都是 20
11.
m = ABCD，n =EFGH
先不考慮 m ＞ n
A + E = 2，3 種情形
B + F = 4，5 種情形
C + G = 6，7 種情形
D + H = 8，9 種情形
所求 = (3 * 5 * 7 * 9 - 3) / 2 = 471
扣掉的 3 種
m = 0，n = 2468
m = n = 1234
m = 2468，n = 0
