Fibonacci Series

A Fibonacci sequence is the integer sequence of 0, 1, 1, 2, 3, 5, 8.... The first two terms are 0 and 1. All other terms are obtained by adding the preceding two terms. This means to say the nth term is the sum of (n-1)th and (n-2)th term.

• In this program, we have to print the Fibonacci sequence using while loop.

Prerequisites

Python 3

Source Code

# Program to display the Fibonacci sequence up to n-th term

nterms = int(input("How many terms? "))

# first two terms
n1, n2 = 0, 1
count = 0

# check if the number of terms is valid
if nterms <= 0:
   print("Please enter a positive integer")
# if there is only one term, return n1
elif nterms == 1:
   print("Fibonacci sequence upto",nterms,":")
   print(n1)
# generate fibonacci sequence
else:
   print("Fibonacci sequence:")
   print(n1, ",", n2, end=', ')
   while count < nterms:
       print(n1)
       nth = n1 + n2
       # update values
       n1 = n2
       n2 = nth
       count += 1

Output

Here, we store the number of terms in nterms. We initialize the first term to 0 and the second term to 1.

If the number of terms is more than 2, we use a while loop to find the next term in the sequence by adding the preceding two terms. We then interchange the variables (update it) and continue on with the process.

You can also solve this problem using recursion:

Source Code

def fibo(n):
    if n <= 1:
        return n
    else:
        return(fibo(n-1)+fibo(n-2))


nterms = int(input("Enter the number of Terms you want: "))
if nterms <= 0:
    print("Please enter a positive integer")
else:
    print("Fibonacci Sequence:")
    for i in range(nterms):
        print(fibo(i))

Output

Author Name

Vikrant