## Wednesday, November 21, 2012

### Celebrating Fibonnacci Day

Fibonacci, or more correctly Leonardo da Pisa (also called Leonardo Bigollo), was born in Pisa, Italy in 1175. He travelled widely in Barbary (Algeria) and was later sent on business trips to Egypt, Syria, Greece, Sicily and Provence.

In 1200 he returned to Pisa and used the knowledge he had gained on his travels to write Liber abaci in which he introduced the Latin-speaking world to the decimal number system.

The Fibonacci Series is a sequence of numbers first created by Leonardo Fibonacci in 1202, introduced in Liber abaci and later named the Fibonacci sequence in his honor. Read more about Fibonacci, Roman numerals and the decimal system on our previous blog post: Fibonacci—810 Years of Mathematical Magic. Leonardo da Pisa (Fibonacci)
Mathematicians celebrate Fibonacci Day on November 23 or 11/23, taking the date from the first four numbers in the Fibonacci sequence shown below. The Fibonacci series begins with 0 or 1. After that, use the simple rule: Add the last two numbers to get the next number in the sequence. See the series in action at thinkquest.org.

This is readily translatable into the following set of equations [3, p4]
• 1 = 1²
• 1 + 3 = 2²
• 1 + 3 + 5 = 3²
• 1 + 3 + 5 + 7 = 4²
• and suggests the general formula:
• 1 + 3 + ... + (2n-1) = n²
From this statement the famous Fibonacci numbers can be derived.
1, 1, 2, 3, 5, 8, 13, 21, 34, 55, 89, 144, 233, 377, 610, 987, ...

where the first two numbers of the series are 1 and 1 and each number afterward is defined as the sum of the two previous terms, Fn = Fn - 2 + Fn - 1. (Though in Fibonacci's sequence the first number was 1 and the second number was two, the first one was assumed.) Read more at plus.maths.org.

If it seems too time-consuming to have to calculate the Fibonacci numbers yourself, use this Fibonacci Calculator. It calculates thousands of Fibonacci numbers exactly and millions upon millions to the first few digits. Click this image to view correlations
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