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1. Print Numbers from 1 to 102. Print All Even Numbers Between 1 and 1003. Sum of First N Natural Numbers4. Print the Factorial of a Given Number5. Print All Odd Numbers Between 1 and 1006. Print Numbers from 10 Down to 17. Print Multiplication Table8. Sum of All Even Numbers Up to N9. Sum of All Odd Numbers Up to N10. Product of Digits11. Count Numbers Divisible by 312. Print Multiples of 5 Up to N13. Sum of Squares Up to N14. Print Alternating Numbers

Sum of First N Natural Numbers

Print the sum of first n natural numbers.

BeginnerPhase 2 - Level 1: Basic LoopingExample 3 of 14
sum-of-first-n-natural-numbers.py
1# Take n as input
2n = int(input("Enter n: "))
3

4# Calculate sum
5sum = 0
6for i in range(1, n + 1):
7    sum += i
8

9print(f"Sum of first {n} natural numbers: {sum}")

Output

Enter n: 5
Sum of first 5 natural numbers: 15

What's going on

Accumulate sum by adding each number.

Key Concepts:

Initialize sum to 0
Loop from 1 to n
Add each number to sum
Formula: n * (n + 1) / 2 (but we use loop)

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