Calculate robots sample

main.rb

def calculate(n)
  [1, 2, 3].repeated_combination(n).to_a.each_with_object({}) { |a, cache|
    Array.new(n) do |i|
      combination = a[0..i]
      if combination.sum == n && !cache.key?(combination)
        cache[combination] = true
      end
    end
  }.keys
end