In this article, we will learn to check whether the given number is a Fibonacci number or not using python.

### Fibonacci series

A Fibonacci sequences is sequences of 0, 1, 1, 2, 3, 5, 8, 13, 21, 34, 55, 89, 144, .....

The first two terms are 0 and 1. All other terms are obtained by adding the preceding two terms.

*F*_{n} = F_{(n-1)} +F_{(n-2)}

#### Program

# Check fibonacci number in python

# import math

import math

# make a function that check the number is perfect square or not

def perfectSquare(x):

s = int(math.sqrt(x))

return s*s == x

# mathe a function that return true for fibonacci series

def is_Fibonacci(n):

# n is Fibonacci if one of 5*n*n + 4 or 5*n*n - 4 or both

# is a perfect square

return perfectSquare(5*n*n + 4) or perfectSquare(5*n*n - 4)

# now check the numbers

for i in range(1,15):

if (is_Fibonacci(i) == True):

print (i,"is a Fibonacci Number")

else:

print (i,"is a not Fibonacci Number ")

# Check fibonacci number in python - docodehere.com

#### Output

1 is a Fibonacci Number
2 is a Fibonacci Number
3 is a Fibonacci Number
4 is a not Fibonacci Number
5 is a Fibonacci Number
6 is a not Fibonacci Number
7 is a not Fibonacci Number
8 is a Fibonacci Number
9 is a not Fibonacci Number
10 is a not Fibonacci Number
11 is a not Fibonacci Number
12 is a not Fibonacci Number
13 is a Fibonacci Number
14 is a not Fibonacci Number