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Arithmetic Sequence Calculator

Online arithmetic sequence calculator: enter first term a₁, common difference d and n to find the nth term.

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a_n=a_1+(n−1)d
First term
Later minus earlier
Positive integer

📖 Tutorial | Arithmetic

1. Definition
An arithmetic sequence has a constant difference d between successive terms; the nth term is a_n=a₁+(n−1)d.
2. Formula & Notation
a₁First term
dCommon difference
3. Properties & Laws
  • a_n=a₁+(n−1)d;
  • d>0 rises, d<0 falls;
  • Arithmetic mean 2b=a+c;
  • a_n=a_m+(n−m)d.
4. Steps
  1. Enter a₁, d, n;
  2. Click "Find Term";
  3. Or click "Load Example".
5. Worked Examples
Example: 2,5,8 (d=3) gives a_10=29.
6. Common Pitfalls
There are n−1 copies of d;
d may be negative;
d = later minus earlier.

❓ FAQ | Arithmetic

Arithmetic?
Constant difference.
Term?
a₁+(n−1)d.
Sign of d?
Positive rises.
Mean?
2b=a+c.
Why n−1?
n−1 additions.
d=0?
Constant sequence.
Find d?
a₂−a₁.