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Uploaded on Sep 30, 2014
Recorded: October 6, 1982
Professor D.H. Lehmer began building electromechanical number sieves with his father in the 1930s. Based on the Sieve of Eratosthenes, these number sieves were used to test prime numbers. Lehmer demonstrates the mathematical processes behind his number sieves, as well as describing Diophantine equations. He then describes the physical processes that can be used to prove primality, starting with the strip method used by Lehmer's father to create a set of stencils. Father and son together created sieves using bicycle chains (1926), 16mm film strips (1936), and steel gears (1932). Later, the younger Lehmer created electronic sieves on his own using delay lines (1966) and shift registers (early 1970s).