No, Pythagoras did not invent the pendulum clock. The pendulum clock was invented by Christiaan Huygens in 1656. Pythagoras was a Greek philosopher and mathematician from around 570 to 495 BC, well known for his contributions to mathematics, particularly for the Pythagorean theorem. While he did study the nature of sound and its mathematical relationships and is often associated with the early study of harmonics, his work predates the invention of clocks by centuries.
The concept of the pendulum and its use in timekeeping was not developed until much later. Huygens’ invention of the pendulum clock significantly improved the accuracy of time measurement and was based on the principles of circular motion and gravity. So, while Pythagoras’s work laid important foundations for mathematics and science, he is not connected to the invention of the pendulum clock.