FIBONACCI

FIBONACCI

Fibonacci and numerals Fibonacci’s real name was Leonardo of Pisa. He introduced Europe to the Arabic numerals we use today—that is 1, 2, 3, and so on. Beforehand, Europeans used cumbersome Roman numerals.

Back in the 12th century, an Italian mathematician named Fibonacci (c. 1170–1250) discovered an extraordinary sequence of numbers. Each number in the sequence is found by simply adding together the previous two. Here’s how it goes: 0, 1, 1, 2, 3, 5, 8, 13, 21, 34, and so on. What’s amazing is just how often this sequence of numbers, called the Fibonacci Numbers, applies to the world around us. 
Fibonacci is best known to the modern world for the spreading of the Hindu–Arabic numeral system in Europe, primarily through the publication in 1202 of his Liber Abaci (Book of Calculation), and for a number sequence named the Fibonacci numbers after him, which he did not discover but used as an example in the Liber Abaci.
Liber Abaci
In the Liber Abaci (1202), Fibonacci introduces the so-called modus Indorum (method of the Indians), today known as Arabic numerals (Sigler 2003; Grimm 1973). The book advocated numeration with the digits 0–9 and place value. The book showed the practical importance of the new numeral system, using lattice multiplication and Egyptian fractions, by applying it to commercial bookkeeping, conversion of weights and measures, the calculation of interest, money-changing, and other applications. The book was well received throughout educated Europe and had a profound impact on European thought.

fibonacci sequence

Liber Abaci also posed, and solved, a problem involving the growth of a population of rabbits based on idealized assumptions. The solution, generation by generation, was a sequence of numbers later known as Fibonacci numbers. The number sequence was known to Indian mathematicians as early as the 6th century, but it was Fibonacci's Liber Abaci that introduced it to the West.

In the Fibonacci sequence of numbers, each number is the sum of the previous two numbers, starting with 0 and 1. This sequence begins 0, 1, 1, 2, 3, 5, 8, 13, 21, 34, 55, 89, 144, 233, 377, 610, 987 ... 

The higher up in the sequence, the closer two consecutive "Fibonacci numbers" of the sequence divided by each other will approach the golden ratio (approximately 1 : 1.618 or 0.618 : 1).