*The symbol π is overloaded in math: depending on context and capitalization, π could be the constant we all know and love (or hate), a projection, a product, or a function. There’s plenty of stuff to read about the circle constant, so today I’m writing about one of those other π’s.*

*Today’s π is the prime counting function. (A prime number is a whole number whose only divisors are one and itself. A prime can’t be written as a product of two other whole numbers in an interesting way.) The function π(x) is pretty easy to understand: for any positive number x, π(x) tells you how many primes there are that are less than or equal to the number x. So π(1) is 0 because there are no primes smaller than 2, π(2)=1 because 2 is prime, π(3)=2 because both 2 and 3 are prime, π(4)=2, and so on.*

Read the full post at Roots of Unity.

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