@robinhouston curious how you hunted. i used

$ grep '^[a-foi]*$' /usr/share/dict/words | tr a-foi a-f01 | while read w ; do echo -n  $w' '; factor $(( 16#$w )) ; done | awk 'nf == 3'

which has bashisms. for slower portability, `$(( 16#$w ))` could be

$(printf '=16\n%s\n' $w | bc)