Arithmetic sequence calculator
In an arithmetic sequence each term goes up by a fixed common difference, like 3, 7, 11. Enter the first term, the difference and n to get the nth term and the sum.
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How to use it
- Enter first term a₁, common difference d and number of terms n.
- The result appears straight away and updates as you edit.
- Copy the result, or copy a link that keeps the same values to share it.
How it is calculated
nth term: aₙ = a₁ + (n - 1) × d. Sum: Sₙ = n × (a₁ + aₙ) ÷ 2.
Example
Inputs: First term a₁ = 3, Common difference d = 4, Number of terms n = 10. Result: Term 10: 39; Sum of the first 10 terms: 210.
Limits and caveats
- n runs from 1 to one million; decimal values use standard floating point precision.
- Only the first 10 terms are listed.
Questions about this tool
How do I find the common difference?
Subtract any term from the next one. In 3, 7, 11 the difference is 7 - 3 = 4.
What is the sum of 1 to 100?
5050: first term 1, difference 1, n = 100, so the sum is 100 × (1 + 100) ÷ 2.
Can the difference be negative?
Yes, then the terms go down, like 10, 7.5, 5 with d = -2.5.