What is the Fibonacci sequence?

Each number is the sum of the two preceding ones: 0, 1, 1, 2, 3, 5, 8, 13, 21, 34... Starting with 0 and 1. The ratio of consecutive Fibonacci numbers approaches the golden ratio φ ≈ 1.618.

How large a Fibonacci number can it generate?

The generator uses BigInt for arbitrary precision. You can generate up to the first 10,000 Fibonacci numbers (the 10,000th has over 2,000 digits).

Fibonacci Generator

Generates the Fibonacci sequence up to a specified number of terms or up to a maximum value. Also checks whether a given number is a Fibonacci number and finds its position in the sequence. Shows the golden ratio approximation as the sequence grows. Supports arbitrary precision for very large Fibonacci numbers using BigInt.

Terms to generate: 20

Starting values

F(0)=0F(0)=1

Fibonacci sequence (20 terms)

01123581321345589144233377610987159725844181

Detailed view

F(0) = 0
F(1) = 1
F(2) = 1
F(3) = 2
F(4) = 3
F(5) = 5
F(6) = 8
F(7) = 13
F(8) = 21
F(9) = 34
F(10) = 55
F(11) = 89
F(12) = 144
F(13) = 233
F(14) = 377
F(15) = 610
F(16) = 987
F(17) = 1597
F(18) = 2584
F(19) = 4181

Enter a term count or maximum value to generate the Fibonacci sequence, or check if a number is Fibonacci.