Which of the giant planets was predicted to exist mathematically before it was ever seen through a telescope?

Name: Which of the giant planets was predicted to exist mathematically before it was ever seen through a telescope?
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Neptune was predicted to exist mathematically before it was observed through a telescope. The irregularities in Uranus' orbit prompted astronomers to hypothesize the presence of another planet, which was later confirmed with Neptune's discovery.

Which of the Giant Planets Was Predicted to Exist Mathematically