What is the next number in this sequence? 0, 1, 1, 2, 3, 5, 8, 13, 21,...
The sequence presented is called the Fibonacci sequence. It was introduced by the Italian mathematician Leonardo of Pisa, well-known as Fibonacci. He wrote a book Liber Abaci where the sequence was introduced to Western European maths for the first time. Before Fibonacci the sequence was observed only in the works of Ancient Indian mathematicians.
After the first two members of the sequence (0, 1) each member is the sum of the two previous members. This sequence usually starts either with 0 and 1 or 1 and 1.