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About

Arithmetic progressions are the foundation of discrete mathematics and sequence analysis. Students and educators often require a reliable method to verify manual calculations of the Nth term and the sum of series. This tool eliminates calculation errors common when dealing with negative integers or decimals.

Understanding the stepwise derivation is critical for algebraic mastery. Rather than simply providing a final number, this calculator breaks down the substitution process into the standard formulas for the general term and the arithmetic series sum. It handles integers, floating-point numbers, and negative differences with precision.

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Formulas

The Nth term of an arithmetic progression is determined by adding the common difference to the first term n-1 times:

an = a1 + (n 1)d

The sum of the first n terms is calculated using the average of the first and last term, multiplied by the count:

Sn = n2 × (2a1 + (n 1)d)

Reference Data

Sequence TypeDescriptionExample ΔCommon Formula
IncreasingTerms grow larger; positive difference (d > 0).2, 5, 8, 11 (d = 3)an = a1 + (n1)d
DecreasingTerms grow smaller; negative difference (d < 0).10, 8, 6, 4 (d = -2)an = a1 + (n1)(d)
ConstantTerms remain unchanged; difference is zero.5, 5, 5, 5 (d = 0)Sn = n × a1
FiniteA sequence with a fixed number of terms.{1, 3, 5, 7}Domain: 1 n N
InfiniteA sequence that continues indefinitely.{2, 4, 6...}n
Gauss's SumSum of first 100 integers.1 to 100S100 = 5050
Odd NumbersSum of the first n odd numbers.1, 3, 5...Sn = n2
Even NumbersSum of the first n even numbers.2, 4, 6...Sn = n(n+1)

Frequently Asked Questions

In sequence theory, n represents the position of a term (1st, 2nd, 3rd). A position cannot be fractional; there is no 2.5th term in a discrete list.
A negative difference causes the terms to decrease. Eventually, terms may become negative. If calculating the sum Sn, adding these negative terms will reduce the total value, potentially resulting in a negative sum for the series.
Yes. While the position n must be an integer, the starting term a₁ and the common difference d can be any real number, including decimals or fractions.
A sequence is an ordered list of numbers. A series is the sum of the terms of a sequence. This tool calculates both the specific term (sequence component) and the total sum (series value).