平方数を除く 2,3,5,6,7,8,10... という数列で、指定番目の数を返す関数

23fig.rb

def fig2(num)
  count = 0
  i = 2
  until count == num
    count += 1 if Math.sqrt(i) != Math.sqrt(i).to_i
    i += 1
  end
  return i - 1
end

def fig3(num)
  i = 2
  j = 1
  until num <= i * j
    i += 1
    j += 1
  end
  return num + j
end

def fig4(num)
  num + Math.sqrt(num + Math.sqrt(num).to_i).to_i
end

def fig5(num)
  1 + num + Math.sqrt(num - Math.sqrt(num).to_i).to_i
end