john_and_ann.rb

def john(n)
  john_and_ann(n)[:john]
end

def ann(n)
  john_and_ann(n)[:ann]
end

def sum_john(n)
    john(n).reduce(:+)
end

def sum_ann(n)
    ann(n).reduce(:+)
end

def john_and_ann(n)
  katas = { john: [0], ann: [1] }
  for k in 1...n
    katas[:john] << k - katas[:ann][katas[:john][k-1]]
    katas[:ann]  << k - katas[:john][katas[:ann][k-1]]
  end
  katas
end