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Geometric Sequence Calculator

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### Discrete Mathematics: Geometric Progressions & Exponential Growth 1. **Multiplicative Ratio**: Each term in a geometric sequence is obtained by multiplying the preceding term by a fixed common.

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⚙ Input Values

📊 Results

Geometric Sequence & Series Summary
a_10 = 39,366 ➔ Finite Sum S_10 = 59,048 | Ratio: 3 | Divergent (|r|≥1) | Formula: a_n = 2 × (3)^(n - 1)
Value of the n-th Term (a_n)
a_10 = 39,366
Sum of First n Terms (Finite Series S_n)
S_10 = 59,048 (Sum of first 10 terms)
Infinite Geometric Series Sum (S_∞ [if |r| < 1])
DIVERGENT (No finite infinite sum because |r| ≥ 1)
Explicit General Formula a_n
a_n = 2 × (3)^(n - 1)
First 10 Terms of the Sequence
2, 6, 18, 54, 162, 486, 1,458, 4,374, 13,122, 39,366
✦ Exponential Progression & Convergence Diagnostic
Geometric Progression Model (a₁ = 2 | r = 3 | n = 10): [1. Target Term Value]: The 10-th term is **a_10 = 39,366**. [2. Finite Series Sum]: The sum of the first 10 terms equals **S_10 = 59,048**. [3. Infinite Series Convergence]: **DIVERGENT (No finite infinite sum because |r| ≥ 1)**. [4. Sequence Expansion]: First terms: **{ 2, 6, 18, 54, 162, 486, 1,458, 4,374, 13,122, 39,366 }**.
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📐 Formula

Geometric Sequence & Series equations:
General n-th Term: a_n = a_1 × r^n-1
Finite Series Sum: S_n = a_1 × ((1 - r^n ÷ 1 - r)) (r 1)
Infinite Series Sum: S_ = (a_1 ÷ 1 - r) (|r| < 1 Convergent)
Common Ratio: r = (a_n ÷ a_n-1)

💡 Practical Example

✅

For example, finding the \(10\text{th term}\) of a geometric sequence starting at \ with common ratio \: The \. The sum of the first 10 terms is \.

📖 About Geometric Sequence Calculator

Discrete Mathematics: Geometric Progressions & Exponential Growth

  • Multiplicative Ratio: Each term in a geometric sequence is obtained by multiplying the preceding term by a fixed common ratio r.
  • Infinite Series Convergence: If |r| < 1), the terms shrink exponentially to zero, allowing the infinite sum to converge to a finite number . If |r| 1, the series diverges to infinity.

How to Use This Calculator

Enter your First Term (a₁) (e.g. 2), Common Ratio (r) (e.g. 3 (multiplier factor)), and Target Term Position to Calculate (n) (e.g. 10 (find the 10th term)). Results update instantly as you type — adjust any value to compare scenarios.

The Formula

Geometric Sequence \& Series equations:

General n-th Term: a_n = a_1 × r^n-1

Finite Series Sum: S_n = a_1 × ((1 - r^n) / (1 - r)) (r ≠ 1)

Infinite Series Sum: S_∞ = (a_1) / (1 - r) (|r| < 1 Convergent)

Common Ratio: r = (a_n) / (a_n-1)

Worked Example

For example, finding the 10th term of a geometric sequence starting at \ with common ratio The \. The sum of the first 10 terms is \.

Understanding Your Result

Evaluate your result in the context of your specific use case and relevant industry standards or reference values. A single calculated result is a starting point — test two to three scenarios to understand how sensitive the outcome is to your key input assumptions. For high-stakes decisions, verify your result against a secondary source or subject-matter expert before acting.

💡 Mathematical Rigor & Applied Context

  • This calculator applies exact mathematical definitions following conventions established by NIST and international standards bodies.
  • Rounding errors accumulate across multi-step calculations. For precision-critical work, maintain extra significant figures through all intermediate steps.
  • Many mathematical concepts have multiple valid formulations — if a result seems unexpected, verify which convention or definition applies to your context.
  • Dimensional analysis (unit tracking) is the fastest way to catch formula errors. Every term in an equation must have consistent, compatible units.
  • Numerical methods used in digital calculators introduce floating-point precision limits (~15 significant digits for IEEE 754 double precision).
  • For statistical and probabilistic calculations, always specify whether you are working with population parameters or sample statistics — formulas differ.
  • Visualizing a problem geometrically or testing with known boundary values (zero, infinity, negative) reveals hidden errors faster than algebraic checking.
  • When in doubt, validate your result against a simplified hand calculation or a published worked example from a textbook or standards document.

Results are for informational and educational purposes only. Always verify critical decisions with a qualified professional.

❓ Frequently Asked Questions

What is the formula for the n-th term of a geometric sequence?

an = a1 × r^(n - 1), where a1 is the first term, r is the common ratio, and n is the term position.

When does an infinite geometric series converge?

An infinite geometric series converges if and only if the absolute value of the common ratio is strictly less than 1 (|r| < 1). The sum is S∞ = a1 ÷ (1 - r).

How do you find the sum of a finite geometric sequence?

Sn = a1 × (1 - r^n) ÷ (1 - r), provided r ≠ 1.

What is the difference between an arithmetic and geometric sequence?

An arithmetic sequence adds a constant difference to each term (linear growth), while a geometric sequence multiplies each term by a constant ratio (exponential growth).

What happens to a geometric sequence if the common ratio is negative?

If r is negative, the terms alternate in sign between positive and negative numbers (an alternating geometric sequence).

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