frons rfons forns ofrns rofns orfns frnos rfnos fnros nfros rnfos nrfos fonrs ofnrs fnors nfors onfrs nofrs ronfs ornfs rnofs nrofs onrfs norfs frosn rfosn forsn ofrsn rofsn orfsn frson rfson fsron sfron rsfon srfon fosrn ofsrn fsorn sforn osfrn sofrn rosfn orsfn rsofn srofn osrfn sorfn frnso rfnso fnrso nfrso rnfso nrfso frsno rfsno fsrno sfrno rsfno srfno fnsro nfsro fsnro sfnro nsfro snfro rnsfo nrsfo rsnfo srnfo nsrfo snrfo fonsr ofnsr fnosr nfosr onfsr nofsr fosnr ofsnr fsonr sfonr osfnr sofnr fnsor nfsor fsnor sfnor nsfor snfor onsfr nosfr osnfr sonfr nsofr snofr ronsf ornsf rnosf nrosf onrsf norsf rosnf orsnf rsonf sronf osrnf sornf rnsof nrsof rsnof srnof nsrof snrof onsrf nosrf osnrf sonrf nsorf snorf
Note: these 'words' (valid or invalid) are all the permutations of the word frons. These words are obtained by scrambling the letters in frons.