Check, if a number i is part of the Fibonacci sequence.

fibonacci.rb

def is_fibonacci?(i)

  sum = [0,1]
  x = 0
  y = 0
  while sum.max <= i 
    sum.length.times do |a|
      x = sum[a] + sum[a-1]

    end
    sum = sum.push(x)
    y +=1
  end
  #puts "#{sum} #{y}"

  sum.include?(i)
  puts "#{sum.max} #{sum.include?(i)}"

end

Thanks for this! The variable y is just for observation yes, no real purpose in the algo?