Calculating the diagonal sum of a number spiral, with '1' in the center.

spiral_numbers.rb

#adds the diagonals of a number spiral (where 1 is center)
def spiral(n)
  sum = 1 
  max = n**2
  corner = 1
  step = 2
  while corner < max
    4.times do |i|
      corner += step
      sum += corner
    end
    step += 2
  end
  sum
end

puts spiral(1001)