Math

Arithmetic Sequence Solver

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

Last validated: 2026-02-14

Arithmetic Sequence Solver computes nth term and partial sums from first term and common difference. It is useful for classwork, exam prep, and quick progression checks in spreadsheets or scripts. The tool avoids manual formula rearrangement errors. Use it to validate sequence calculations quickly.

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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.

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 use this tool

Enter first term, common difference, and term index or count.
Run the solver to compute term values and sums.
Cross-check results against your expected formula setup.

Worked Example

Auto-generated from the tool's current default or entered inputs.

Example Inputs

First term: 3.0
Common difference: 2.0
N: 10
Nth term: 21.0

Expected Outputs

First term: 3
Common difference: 2
N: 10
Nth term: 21

Interpretation

First term is 3.0. Use this as a decision input, not as a standalone conclusion.
Common difference is 2.0. Use this as a decision input, not as a standalone conclusion.
N is 10. Use this as a decision input, not as a standalone conclusion.
Interpret this value alongside sample quality and assumptions to avoid overconfidence.

Scenario Compare (A vs B)

Use this to compare two input sets and quantify change in key outputs.

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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