regular expression for mod 3 =1

Question

someone can help me found the regular expression of

L={σ×w, σϵ∑={a, b},#σ(w)mod 3 = 1}

 

tnx.

Comments

can you write your language clearly, i didn't understood your language,

you may enumerate the strings of your language.

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i need to find the regular expression of all the a,b that with give me mod 3 = 1

like : 1,4,7,10,,,,,,,,

(a+b) + (bb + aa)(ab+ba).....

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then check (a+b).[ (a+b).(a+b).(a+b)]*

Answer 1

look its always better that you should form the automata first then reduce it to the regex.

further as pointed out the regex will be  { ( a+b) (a+b) (a+b) }* (a+b)

Comments

thank you both all good