Fibonacci number

![The Fibonacci spiral: an approximation of the golden spiral created by drawing circular arcs connecting the opposite corners of squares in the Fibonacci tiling;[4] this one uses squares of sizes 1, 1, 2, 3, 5, 8, 13, 21, and 34.](/uploads/202501/13/Fibonacci_spiral_34.svg3455.png)


In mathematics, the Fibonacci numbers or Fibonacci sequence are the numbers in the following integer sequence:
or (often, in modern usage):
By definition, the first two numbers in the Fibonacci sequence are either 1 and 1, or 0 and 1, depending on the chosen starting point of the sequence, and each subsequent number is the sum of the previous two.