Number Sequence Calculator
Build arithmetic, geometric or Fibonacci sequences. See the terms, the nth term, and the sum of the series.
Sequence settings
How to use this calculator
1. Choose a sequence type
Pick arithmetic, geometric or Fibonacci. The input fields change to match — for example, geometric asks for a ratio while arithmetic asks for a difference.
2. Enter the starting values
Give the first term and the rule (difference or ratio), or for Fibonacci the first two terms. Then set how many terms you want to generate.
3. Read the terms, nth term and sum
The full list appears as a comma-separated series, with the value of the last (nth) term and the total of all terms shown beneath it.
4. Long sequences are trimmed
To keep the page readable, only the first 60 terms are listed. A note appears when the sequence is longer; the nth term and sum still use the full count you entered.
About number sequences
Arithmetic vs geometric
An arithmetic sequence adds a fixed common difference each step (2, 5, 8, 11), while a geometric sequence multiplies by a fixed common ratio (3, 6, 12, 24). The growth pattern is steady for one and exponential for the other.
The nth term
For arithmetic, aₙ = a + (n − 1)d. For geometric, aₙ = a · r⁽ⁿ⁻¹⁾. These formulas jump straight to any term without listing the ones before it.
The Fibonacci sequence
Each Fibonacci term is the sum of the two before it, classically starting 0, 1, 1, 2, 3, 5, 8. You can change the first two terms here to explore related sequences such as the Lucas numbers.