Browse

FACTDOUBLE Function (LibreOffice Calc)

Math Intermediate LibreOffice Calc LibreOffice 3.0

The FACTDOUBLE function in LibreOffice Calc returns the double factorial of a non‑negative integer. It is essential in combinatorics, probability, special functions, and advanced mathematical modeling.

The **FACTDOUBLE** function returns the *double factorial* of a non‑negative integer in LibreOffice Calc. The double factorial grows more slowly than the standard factorial and is widely used in combinatorics, probability, special functions, and advanced mathematical modeling. FACTDOUBLE pairs naturally with `FACT`, `COMBIN`, and `PERMUT`.

This guide provides syntax, examples, advanced usage patterns, common errors, and best practices, making it one of the most complete FACTDOUBLE references available for LibreOffice Calc.

What the FACTDOUBLE Function Does

  • Computes the double factorial of a non‑negative integer
  • Defined as:
    n!! = n × (n‑2) × (n‑4) × …
  • Even and odd numbers follow different sequences
  • Used in combinatorics, probability, and special functions

It is designed to be precise, efficient, and universally compatible.

Syntax

FACTDOUBLE(number)

Arguments

  • number:
    A non‑negative integer.
    Non‑integer values are truncated.

Basic Examples

Double factorial of an even number

=FACTDOUBLE(8)

Computes: 8 × 6 × 4 × 2 = 384.

Double factorial of an odd number

=FACTDOUBLE(7)

Computes: 7 × 5 × 3 × 1 = 105.

Double factorial of zero or negative one

=FACTDOUBLE(0)

Returns 1.

=FACTDOUBLE(-1)

Returns 1.

FACTDOUBLE with non‑integer input

=FACTDOUBLE(7.9)

Equivalent to FACTDOUBLE(7) → returns 105.

Advanced Examples

Relationship to standard factorial (even n)

=FACT(A1) / (2^(A1/2) * FACT(A1/2))

Equivalent to FACTDOUBLE(A1) when A1 is even.

Relationship to standard factorial (odd n)

=FACT(A1) / (2^((A1-1)/2) * FACT((A1-1)/2))

Equivalent to FACTDOUBLE(A1) when A1 is odd.

Double factorial for permutations of perfect matchings

=FACTDOUBLE(A1 - 1)

Used in combinatorics of pairings.

Double factorial in probability distributions

=FACTDOUBLE(2*A1 - 1)

Appears in normal distribution integrals and special functions.

Double factorial for geometric formulas

=FACTDOUBLE(2*A1 - 1) / (2^A1)

Used in spherical volume and surface area formulas.

Manual double factorial using PRODUCT

=PRODUCT(A1; A1-2; A1-4; ...)

Equivalent to FACTDOUBLE(A1).

Double factorial for binomial expansions

=FACTDOUBLE(2*A1 - 1) / FACTDOUBLE(2*A1)

Used in advanced combinatorial identities.

Common Errors and Fixes

Err:502 — Invalid argument

Occurs when:

  • number is negative (other than -1)
  • number is text
  • number cannot be coerced to a non‑negative integer

Err:503 — Overflow

Occurs when:

  • number is too large
  • double factorial exceeds Calc’s numeric limit

FACTDOUBLE returns unexpected results

Cause:

  • Non‑integer values are truncated
    Example: FACTDOUBLE(6.8) → FACTDOUBLE(6) → 48.

Best Practices

  • Use FACTDOUBLE for combinatorics and special functions
  • Avoid large inputs (double factorials grow rapidly)
  • Use FACT for standard factorials
  • Use COMBIN and PERMUT for structured combinatorics
  • Use PRODUCT for manual double factorials
Double factorials appear in surprising places — from combinatorics to geometry to probability. FACTDOUBLE gives you a clean, efficient way to compute them.
  • Use FACT for standard factorials
  • Use COMBIN for combinations
  • Use COMBINA for combinations with repetition
  • Use PERMUT for permutations
  • Use PERMUTATIONA for permutations with repetition
  • Use PRODUCT(A1; A1-2; …) for manual double factorials

By mastering FACTDOUBLE and its related combinatorics functions, you can build powerful probability, counting, and number theory models in LibreOffice Calc.

Reproducible example (tested in LibreOffice Calc)

This standalone example was calculated in LibreOffice Calc 25.2.3.2 and matched the expected value. It is a practical cross-check of one usage, not proof that every example elsewhere on this page is correct.

=FACTDOUBLE(5)

Expected result: 15.

Multiply every second integer down to one.

If the result differs, check the referenced cells, argument separators and number formatting. For more information, consult the LibreOffice Calc official help.