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Department ofMathematics and Computer Science

Stories

Students Publish on Primality Testing

Professor Emeritus Schaefer, Junhyun Lim (Mathematics & Computer Science) and Shaunak Mashalkar (Mathematics & Computer Science and Engineering) find new methods for creating many Fibonacci pseudoprimes.

In Winter 2020, visiting professor Carl Pomerance challenged his Number Theory class to either find a positive integer that is a Baille-PSW pseudoprime, or prove that none exists. There is a $620 prize for the resolution of this problem. A pseudoprime is an integer that, in some ways, acts like a prime number, but is, in fact, composite. A Baille-PSW pseudoprime is a Fibonacci pseudoprime that satisfies two other properties. If none exists, then this would give an extremely fast way of testing half of all odd numbers for primality. After the course was over, two of the students, Junhyun Lim (Mathematics & Computer Science) and Shaunak Mashalkar (Mathematics & Computer Science and Engineering) asked Professor Schaefer for help solving this problem.

They found new methods for creating many Fibonacci pseudoprimes. They then tested 2^31 of them to see if any of them were Baille-PSW pseudoprimes – alas, none were. They wrote an article explaining their new methods and their search for a Baille-PSW pseudoprime and the article has been accepted by The Fibonacci Quarterly, a journal once published out of SCU.

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