Problem

Source: China TST 2003

Tags: algebra unsolved, algebra



$m$ and $n$ are positive integers. Set $A=\{ 1, 2, \cdots, n \}$. Let set $B_{n}^{m}=\{ (a_1, a_2 \cdots, a_m) \mid a_i \in A, i= 1, 2, \cdots, m \}$ satisfying: (1) $|a_i - a_{i+1}| \neq n-1$, $i=1,2, \cdots, m-1$; and (2) at least three of $a_1, a_2, \cdots, a_m$ ($m \geq 3$) are pairwise distince. Find $|B_n^m|$ and $|B_6^3|$.