Generate letters to represent number using ruby?

Question

I would like to generate a sequence of letters i.e. \"A\", \"DE\" \"GJE\", etc. that correspond to a number. The first 26 are pretty easy so 3 returns \"C\", 26 returns \"Z\

Answer 1

def letter_sequence(n)
    n.to_s(26).each_char.map {|i| ('A'..'Z').to_a[i.to_i(26)]}.join
end