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Number Sequence Calculator

Find the nth term of an arithmetic or geometric sequence.

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What Number Sequence Calculator does

An arithmetic sequence adds a fixed amount each step; a geometric sequence multiplies by a fixed ratio. Those two patterns cover a great deal of school mathematics and a fair amount of financial arithmetic.

Give the first term, the difference or ratio, and the position you want, and the term is calculated directly rather than by counting through.

  • Arithmetic sequences from a first term and common difference
  • Geometric sequences from a first term and common ratio
  • Direct calculation of any term position

How to use Number Sequence Calculator

  1. 1

    Choose the sequence type

    Arithmetic if each term adds a constant; geometric if each term multiplies by one.

  2. 2

    Enter the first term and the step

    The common difference for arithmetic, the common ratio for geometric.

  3. 3

    Enter the position

    The nth term is calculated from the formula, not by iteration.

Example

The same starting point, two patterns

Input

First term 2, step 3, n = 5

Output

Arithmetic (add 3):      2, 5, 8, 11, 14   → 14
Geometric (multiply 3):  2, 6, 18, 54, 162  → 162

Limits and known behaviour

  • Arithmetic and geometric sequences only. Fibonacci, quadratic and recursively defined sequences are not supported.
  • The nth term is returned; the sum of the series is not.
  • The sequence itself is not listed.
  • Geometric sequences grow extremely fast, and a large n can exceed the range where results stay precise.

Privacy and data handling

Runs entirely in your browser

  • The calculation runs in this page. Nothing you enter is transmitted or stored.
  • The tool works offline once the page has loaded.

Site-wide data handling, including analytics and advertising, is described in the privacy policy.

Frequently asked questions

How do I tell which type my sequence is?

Look at consecutive terms. If the difference between them is constant it is arithmetic; if the ratio between them is constant it is geometric. If neither, it is a different kind of sequence.