What is the man who defined The chromatic polynomial best known for?
Chromatic polynomial: The chromatic polynomial is a polynomial studied in algebraic graph theory, a branch of mathematics. Chromatic polynomial:  It counts the number of graph colorings as a function of the number of colors and was originally defined by George David Birkhoff to attack the four color problem. George David Birkhoff: George David Birkhoff (March 21, 1884 – November 12, 1944) was an American mathematician best known for what is now called the ergodic theorem.
the ergodic theorem