Sum of First N Natural Numbers
Compute the sum of the first N natural numbers using a formula.
BeginnerTopic: Basic Python Programs
What You'll Learn
- Using mathematical formulas for summation
- Applying integer division for exact results
- Validating that N is positive
Python Sum of First N Natural Numbers Program
This program helps you to learn the fundamental structure and syntax of Python programming.
# Program to find the sum of first N natural numbers
n = int(input("Enter a positive integer N: "))
if n <= 0:
print("Please enter a positive integer.")
else:
total = n * (n + 1) // 2
print("Sum of first", n, "natural numbers is:", total)Output
Enter a positive integer N: 10 Sum of first 10 natural numbers is: 55
Step-by-Step Breakdown
- 1Read N from the user.
- 2Check that N is positive.
- 3Apply the formula N * (N + 1) // 2.
- 4Print the resulting sum.
Understanding Sum of First N Natural Numbers
We use the well-known formula:
\[ 1 + 2 + 3 + \dots + N = \frac{N(N+1)}{2} \]
Using integer division // ensures we get an integer result when N is an integer.
Note: To write and run Python programs, you need to set up the local environment on your computer. Refer to the complete article Setting up Python Development Environment. If you do not want to set up the local environment on your computer, you can also use online IDE to write and run your Python programs.