My code to find the sum of first x natural numbers

Question

Please check and correct me
https://code.sololearn.com/c88nm8EtOIev/?ref=app

Answer 1

I wrote this program to solve the problem without looping. It is similar in principle to the formula given by Jan Markus, though I generalized it to work between any range of integers. I included a brief explanation in the comments at the end to show how it works.

https://code.sololearn.com/cxQki21ZMDIX/?ref=app

Answer 2

Jan Markus, excellent!

I considered exploring that approach to see whether it could simplify the code, but I hadn't done the math yet. Much appreciated.

Answer 3

https://code.sololearn.com/c8ntnh7W4FUX/?ref=app