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Python | sympy.fibonacci() method

  • Last Updated : 14 Jul, 2019
Geek Week

With the help of sympy.fibonacci() method, we can find the Fibonacci number and Fibonacci polynomial in SymPy.

fibonacci(n) -
The Fibonacci numbers are the integer sequence defined by the initial terms F_0 = 0, F_1 = 1 and the two-term recurrence relation F_n = F_{n-1} + F_{n-2}.

Syntax: fibonacci(n)

Parameter:
n – It denotes the number upto which Fibonacci number is to be calculated.



Returns: Returns the nth Fibonacci number.

Example #1:




# import sympy 
from sympy import * 
  
n = 7
print("Value of n = {}".format(n))
   
# Use sympy.fibonacci() method 
nth_fibonacci = fibonacci(n)  
      
print("Value of nth fibonacci number : {}".format(nth_fibonacci))  

Output:

Value of n = 7
Value of nth fibonacci number : 13

fibonacci(n, k) -

The Fibonacci polynomials are defined by F_1(k) = 1, F_2(k) = k, and F_n(k) = k*F_{n-1}(k) + F_{n-2}(k) for n > 2. For all positive integers n, F_n(1) = F_n.

Syntax: fibonacci(n, k)

Parameter:
n – It denotes the nth Fibonacci polynomial.
k – It denotes the variable in the Fibonacci polynomial.



Returns: Returns the the nth Fibonacci polynomial in k, Fn(k)

Example #2:




# import sympy 
from sympy import * 
  
n = 5
k = symbols('x')
print("Value of n = {} and k = {}".format(n, k))
   
# Use sympy.fibonacci() method 
nth_fibonacci_poly = fibonacci(n, k)  
      
print("The nth fibonacci polynomial : {}".format(nth_fibonacci_poly))  

Output:

Value of n = 5 and k = x
The nth fibonacci polynomial : x**4 + 3*x**2 + 1

Example #3:




# import sympy 
from sympy import * 
  
n = 6
k = 3
print("Value of n = {} and k = {}".format(n, k))
   
# Use sympy.fibonacci() method 
nth_fibonacci_poly = fibonacci(n, k)  
      
print("The nth fibonacci polynomial value : {}".format(nth_fibonacci_poly))  

Output:

Value of n = 6 and k = 3
The nth fibonacci polynomial value : 360

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