バードの配列表記
Rule M3. { a , 1 # } = a {\displaystyle \{a,1\#\}=a}
Rule M4. { a , b [ m 1 ] 1 [ m 2 ] ⋯ 1 [ m x ] c # } = { a ⟨ m 1 ⟩ b [ m 1 ] a ⟨ m 2 ⟩ b [ m 2 ] ⋯ a ⟨ m x ⟩ b [ m x ] ( c − 1 ) # } {\displaystyle \{a,b[m_{1}]1[m_{2}]\cdots 1[m_{x}]c\#\}=\{a\langle m_{1}\rangle b[m_{1}]a\langle m_{2}\rangle b[m_{2}]\cdots a\langle m_{x}\rangle b[m_{x}](c-1)\#\}}
Rule M5. { a , b [ m 1 ] 1 [ m 2 ] ⋯ 1 [ m x ] 1 , 1 , ⋯ , 1 , 1 , c # } = { a ⟨ m 1 ⟩ b [ m 1 ] a ⟨ m 2 ⟩ b [ m 2 ] ⋯ a ⟨ m x ⟩ b [ m x ] a , a , ⋯ , 1 , 1 , c − 1 # } {\displaystyle \{a,b[m_{1}]1[m_{2}]\cdots 1[m_{x}]1,1,\cdots ,1,1,c\#\}=\{a\langle m_{1}\rangle b[m_{1}]a\langle m_{2}\rangle b[m_{2}]\cdots a\langle m_{x}\rangle b[m_{x}]a,a,\cdots ,1,1,c-1\#\}}