Formula

General Term of an Arithmetic Sequence

The general term (nnth term) of an arithmetic sequence provides a formula for calculating the value of any term directly from its position number, the first term, and the common difference. For an arithmetic sequence with first term a1a_1 and common difference dd, the nnth term is given by:

an=a1+(n1)da_n = a_1 + (n - 1)d

This formula arises from the pattern that each successive term adds one more copy of dd to the first term: the 1st term equals a1+0da_1 + 0d, the 2nd term equals a1+1da_1 + 1d, the 3rd term equals a1+2da_1 + 2d, and so on. In general, the number of times dd is added is always one less than the term's position number.

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Updated 2026-05-26

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