# The Book of Squares

The Book of Squares, (Liber Quadratorum[1] in the original Latin) is a book on algebra by Leonardo Fibonacci, published in 1225. It was dedicated to Frederick II, Holy Roman Emperor.[2] Fibonacci's identity, establishing that the set of all sums of two squares is closed under multiplication, appears in it. The book anticipated the works of later mathematicians like Fermat and Euler.[3] The book examines several topics in number theory,[4] among them an inductive method for finding Pythagorean triples based on the sequence of odd integers, the fact that the sum of the first ${\displaystyle n}$ odd integers is ${\displaystyle n^{2}}$, and the solution to the congruum problem.