102       strings from the language $\{a^n\;|\;\exists k.\; n = 3 k

   102       strings from the language $\{a^n\;|\;\exists k.\; n = 3 k

   103       + 1 \}$. 

   103       + 1 \}$. 

   104       

   104       

   105 \item Give a regular expression that can recognise an odd 

   105 \item Give a regular expression that can recognise an odd 

   106 number of $a$s or an even number of $b$s.     

   106 number of $a$s or an even number of $b$s.     

   108 \end{enumerate}

   109 \end{enumerate}

   109 

   110 

   110 \end{document}

   111 \end{document}

   111 

   112 

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