htbn thbn hbtn bhtn tbhn bthn htnb thnb hntb nhtb tnhb nthb hbnt bhnt hnbt nhbt bnht nbht tbnh btnh tnbh ntbh bnth nbth
Note: these 'words' (valid or invalid) are all the permutations of the word htbn. These words are obtained by scrambling the letters in htbn.