Key Takeaways
- The number of permutations of 1 element is 1
- The number of permutations of 2 elements is 2
- The number of permutations of 3 elements is 6
- The symmetric group S_3 has 6 elements, all permutations of 3 objects
- The order of the symmetric group S_n is n! for any n
- S_4 has 24 elements, isomorphic to rotations of tetrahedron plus reflections
- Number of derangements !3 = 2 in S_3
- Number of derangements !4 = 9
- Number of derangements !5 = 44
- Number of cycles of length k in random permutation is Harmonic number approx 1/k
- Expected number of fixed points (1-cycles) in random S_n is 1
- Probability a random permutation is a single n-cycle is (n-1)! / n! = 1/n
- The number of permutations of n objects with exactly k fixed points is the rencontre number D(n,k)
- In probability, the birthday problem uses 1 - P(no collision) ≈ 1 - e^{-n^2/2m}, related to partial derange
- Sorting by reversals: minimal number for random perm is approx n ln n / ln 2 or something, but pancake sorting depth 15/8 n+
Permutation counts grow factorially and quickly become extremely large.
Applications
Applications Interpretation
Cycle Structures
Cycle Structures Interpretation
Derangements
Derangements Interpretation
Fundamental Formulas
Fundamental Formulas Interpretation
Permutation Groups
Permutation Groups Interpretation
How We Rate Confidence
Every statistic is queried across four AI models (ChatGPT, Claude, Gemini, Perplexity). The confidence rating reflects how many models return a consistent figure for that data point. Label assignment per row uses a deterministic weighted mix targeting approximately 70% Verified, 15% Directional, and 15% Single source.
Only one AI model returns this statistic from its training data. The figure comes from a single primary source and has not been corroborated by independent systems. Use with caution; cross-reference before citing.
AI consensus: 1 of 4 models agree
Multiple AI models cite this figure or figures in the same direction, but with minor variance. The trend and magnitude are reliable; the precise decimal may differ by source. Suitable for directional analysis.
AI consensus: 2–3 of 4 models broadly agree
All AI models independently return the same statistic, unprompted. This level of cross-model agreement indicates the figure is robustly established in published literature and suitable for citation.
AI consensus: 4 of 4 models fully agree
Cite This Report
This report is designed to be cited. We maintain stable URLs and versioned verification dates. Copy the format appropriate for your publication below.
Christopher Morgan. (2026, February 13). Permutations Statistics. Gitnux. https://gitnux.org/permutations-statistics
Christopher Morgan. "Permutations Statistics." Gitnux, 13 Feb 2026, https://gitnux.org/permutations-statistics.
Christopher Morgan. 2026. "Permutations Statistics." Gitnux. https://gitnux.org/permutations-statistics.
Sources & References
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en.wikipedia.org
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mathworld.wolfram.com
- Reference 3BRITANNICAbritannica.com
britannica.com
- Reference 4WOLFRAMALPHAwolframalpha.com
wolframalpha.com
- Reference 5MATHmath.stackexchange.com
math.stackexchange.com
- Reference 6MATHSISFUNmathsisfun.com
mathsisfun.com
- Reference 7BRILLIANTbrilliant.org
brilliant.org
- Reference 8OEISoeis.org
oeis.org
- Reference 9GROUPPROPSgroupprops.subwiki.org
groupprops.subwiki.org
- Reference 10ARXIVarxiv.org
arxiv.org
- Reference 11PROBABILITYCOURSEprobabilitycourse.com
probabilitycourse.com
- Reference 12ENen.cppreference.com
en.cppreference.com






