Collatz Sequence - find longest chain of collatz values from 1 to 1,000,000

collatz.rb

def collatz(n)
  length = 1
  
  loop do
    if n == 1
      return length
    end
    if n % 2 == 0
      n = n / 2
    else
      n = (3*n) + 1
    end
    length += 1
  end
  
end

longest = 0
longest_n = nil

(1..1000000).each do |n|
  length = collatz(n)
  if length > longest
    longest = length
    longest_n = n
  end
end

puts longest
puts longest_n