The sum of natural numbers means adding together the counting numbers starting from 1, such as 1 2 3 4 and so on. For example, the sum of the first five natural numbers is 15. At first, this looks like a simple counting task, but there is a clear pattern behind it. Instead of adding each number one by one, we can use a shortcut: multiply the number of terms by the next number and divide by two. This works because the numbers can be paired from opposite ends of the list, like 1 with 5, 2 with 4,