fib.rb

def fib(n)
  if n <= 2
    return (1..n).to_a
  else
  k = n - 2
  arr = [1,2] 
    k.downto(2).each do |j|
      i = arr[-2]+arr[-1]
      arr = arr.push(i) if i < 4000000
    end
  end
  return arr
end

fib(1000).select { |k| k.even? }.inject(:+)