About the Sequence Sum Calculator
Sum of the first n natural numbers, squares, cubes, odd or even numbers using closed-form formulas.
Also known as: sum of natural numbers, sum of squares, sum of cubes, sigma sum, sum 1 to n.
How to use this calculator
- Enter series, n.
- The result updates instantly as you type — press Calculate (or Enter) at any time.
- Open “Step-by-step” to see how the answer was worked out.
- Use Copy result or Share to save the answer or send a link with your inputs.
Formula
Σk = n(n+1)/2 · Σk² = n(n+1)(2n+1)/6 · Σk³ = [n(n+1)/2]²
Worked example
Using the values pre-filled in the calculator above:
- Series: 1 + 2 + … + n
- n = 100
the calculator returns:
- Sum: 5,050
Working
Formula: n(n+1)/2 with n = 100