An arithmetic sequence (or progression) is a sequence of numbers such that the difference between consecutive terms is constant. This constant is called the common difference (d).

Key Formulas:

• N-th Term (aₙ): To find any term in the sequence.
  \(a_n = a_1 + (n-1)d\)
• Sum of the First n Terms (Sₙ): To find the sum of a part of the sequence.
  \(S_n = \frac{n}{2}(a_1 + a_n)\)
  or
  \(S_n = \frac{n}{2}(2a_1 + (n-1)d)\)

This calculator can solve for any of the variables (\(a_n, S_n, a_1, d, n\)) if you provide the others.