Fibonacci Numbers
Fibonacci Sequence
Numbers characterized by the fact that every number after the first two is the sum of the two preceding ones, in the following sequence: 1, 1, 2, 3, 5, 8, etc.
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Origin
The sequence was first described in the West by Leonardo of Pisa — known as Fibonacci — in his 1202 book Liber Abaci, where it appeared as a puzzle about the growth of a rabbit population. The same pattern had, however, been described centuries earlier in Indian mathematics: the scholar Pingala identified it around 200 BCE while counting syllable patterns in Sanskrit prosody. The name "Fibonacci sequence" was itself coined in 1838 by the Franco-Italian historian Guillaume Libri.
Updated February 22, 2026