Math

Arithmetic Sequence Solver

Find nth term and sum of an arithmetic progression from a, d, and n.

Formula reviewed: 2026-02-14 Math

Use this free online Arithmetic Sequence Solver to compute nth term and partial sums from first term and common difference. It is useful when you need a focused browser-based utility that turns a specific set of inputs into a practical result quickly. The form focuses on First term (a), Difference (d), n and returns Sequence Inputs, Results, so you can move from input to answer without setting up a spreadsheet or custom script. Run one realistic example, adjust the inputs, and compare how the result changes before you copy or share it. Save the inputs with the result when the output will be shared, audited, or used as part of a larger workflow.

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Input Pattern

Enter values in the left panel, keep units explicit, run the calculation, then copy or share the result. Invalid fields are highlighted immediately.

How to use this tool

Enter First term (a), Difference (d), n for the arithmetic sequence solver, keeping units, dates, or text format consistent with the form labels.
Check optional fields and assumptions before running so the result matches the workflow you have in mind.
Click "Run the tool" and review Sequence Inputs, Results for the primary output.
Copy or share the result together with the inputs so the output can be reproduced later.

Sequence Inputs

For arithmetic progression: a, d, n.

Results

Nth term: 21.000000

Sum of first n terms: 120.000000

Preview terms: 3.0, 5.0, 7.0, 9.0, 11.0, 13.0, 15.0, 17.0, 19.0, 21.0

How to interpret the result

First term is 3.0. Compare it with the assumptions and units shown on this page before using it in a workflow.
Common difference is 2.0. Compare it with the assumptions and units shown on this page before using it in a workflow.
N is 10. Compare it with the assumptions and units shown on this page before using it in a workflow.
Interpret this value alongside sample quality and assumptions to avoid overconfidence.

Confidence and limitations

Outputs are deterministic formula results and depend entirely on input quality and units.
Results are for planning and learning; verify with domain standards before safety-critical use.
Rounding and finite precision can introduce small differences in edge cases.

Formula References

Algebra and arithmetic identities used by the selected formula.
Standard precision arithmetic; rounding shown for readability.

Assumptions

Outputs are deterministic formula results and depend entirely on input quality and units.
Results are for planning and learning; verify with domain standards before safety-critical use.
Rounding and finite precision can introduce small differences in edge cases.

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