Editing De Bruijn sequence (section)

==f-fold de Bruijn sequences==
An '''f-fold n-ary de Bruijn sequence''' is an extension of the notion ''n''-ary de Bruijn sequence, such that the sequence of the length <math>fk^n</math> contains every possible [[subsequence]] of the length ''n'' exactly ''f'' times. For example, for <math>n=2</math> the cyclic sequences 11100010 and 11101000  are two-fold binary de Bruijn sequences. The number of two-fold de Bruijn sequences, <math>N_n</math> for <math>n=1</math> is <math>N_1=2</math>, the other known numbers{{sfnp|Osipov|2016}} are <math>N_2=5</math>, <math>N_3=72</math>, and <math>N_4=43768</math>.