What this calculator does
Arithmetic sequence works out the nth term and the sum of the first n terms of an arithmetic sequence. Enter your own figures above and the answer updates as you type: nothing is fixed in the code, so the result reflects exactly the numbers you supply.
The formula this calculator evaluates is printed under the tool and explained below, so you can check the working by hand or reuse it in a spreadsheet.
The formula
Formulaaₙ = a₁ + (n−1)d; Sₙ = n/2 × (2a₁ + (n−1)d)
The inputs explained
| Field | What to enter |
|---|---|
| First term (a₁) | A number. Starts at 5. |
| Common difference (d) | A number. Starts at 3. |
| Term number (n) | A number. Starts at 10. |
Worked examples
Every figure in the tables below is produced by this page’s own calculator at build time, so the numbers and the tool always agree. Select any row to load that scenario.
How the answer changes with first term (a₁)
Every other input is held at the calculator’s starting values while first term (a₁) varies. Select any row to load that scenario into the calculator.