Project Euler 14 in ruby

@table = {1 => 1}

result = [0,0]

def next_number(n)
  if n.even?
    n / 2
  else
    3 * n + 1
  end
end

def sequence(n)
  prev_value = @table[n]
  if prev_value
    prev_value
  else
    @table[n] = 1 + sequence( next_number(n) )
  end
end



1_000_000.downto(1) do |n|
  seq = sequence(n)
  if seq > result[1]
    result = [n, seq]
  end
end