Leonardo Pisano,

known as “Fibonacci”

Leonardo Pisano, son of Guglielmo Bonacci—hence the nickname Fibonacci—lived in Pisa between 1170 and 1240. Revered as one of the greatest mathematicians of all time, he was introduced to Arabic mathematics during travels with his father, a representative of the merchants of the maritime republic of Pisa, in North Africa. It was in Algeria that Fibonacci studied and mastered the Indo-Arabic numerical system, a precursor to the modern decimal system, based on ten digits from 0 to 9.

Fibonacci recognized the greater practicality of this system compared to the Roman numerals in use at the time. Through his four books, including the “Liber Abaci” published in 1202, he introduced the decimal system as we know it today.

In the same book, he also presented the numerical sequence now famously known as the “Fibonacci Sequence,” though it had long been known to Arab and Hindu mathematicians. However, it was only in the 19th century that the French mathematician Lucas named it after its first European promoter.

The Fibonacci Sequence is a series of positive integers where each number is the sum of the two preceding ones: for example, 1, 1, 2, 3, 5, 8, 13, 21, 34, 55, and so on. This type of progression is also observed in nature, especially in growth patterns, such as the arrangement of leaves along a plant stem, the spiral arrangement of seeds in a sunflower, or in the fractal shapes of many shells.

The Fibonacci sequence has connections with other mathematical concepts like the Golden Ratio and its algebraic value known as the “Phi number (φ),” which appears in numerous natural forms and consequently in countless works of art since ancient Greece. One of the most well-known graphical representations is the Fibonacci Spiral, which depicts the union of squares with side lengths corresponding to the numbers in the sequence.