Python Program to Calculate Sum of Natural Numbers.

Natural numbers are a set of positive integers starting from 1 and continuing indefinitely. They are the numbers you use for counting and ordering. The sum n natural numbers can be calculated using a formula or by using a loop. 

Example:

Input: n = 5
Output: 15

Explanation:
1+2+3+4+5 = 15

The sum of Natural Numbers Using a Loop.

You can easily find the sum of natural numbers using a for or a while loop in Python.

Algorithm:

• Take the input value n from the user.

• Initialize a variable S to 0 (to store the sum).

• Use a for loop to iterate from 1 to n. In each iteration, add the current number to S.

• Display the sum of n natural numbers as a result.

Python Code to Find Sum of Natural Numbers Using for loop.

# Python code implementation to find sum of natural numbers
def sum_of_natural_numbers_with_loop(n):
    S = 0
    for i in range(1, n + 1):
        S += i
    return S

n = int(input("Enter the value of n: "))

result = sum_of_natural_numbers_with_loop(n)

print(f"Sum of the first {n} natural numbers using a loop is: {result}")

Output:

Enter the value of n: 10
sum of the first 10 natural numbers using a loop is: 55

The Sum of Natural Numbers Using Math.

The most efficient way to find the sum of natural numbers is by using a math formula. Formula: sum = n*(n+1)/2

Example:

Input: n = 10;
Output: 55

Explanation: 
sum = n*(n+1)/2
    = 10*(10+1)/2
    = 10*(11)/2
    = 10*5.5
    = 55

Algorithm:

• Take the value of n as an input from the user.

• Initialize a variable sum to 0 to store the sum of natural numbers.

• Use the mathematical formula to calculate the sum and store the result in the sum variable.

• Display the value of the sum as a result. 

Python code to find the sum of natural numbers using a formula.

# Python sum of natural numbers
def sum_of_natural_numbers(n):
    S = (n * (n + 1)) // 2
    return S

n = int(input("Enter the value of n: "))

result = sum_of_natural_numbers(n)

print(f"Sum of the first {n} natural numbers is: {result}")

Output:

Enter the value of n: 10
sum of the first 10 natural numbers using a loop is: 55

These are the two Python program that calculates the sum of the first n natural numbers.

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