combinatorics

Introduction
History
- Early developments
- Combinatorics during the 20th century
Problems of enumeration
- Permutations and combinations
  - Binomial coefficients
  - Multinomial coefficients
- Recurrence relations and generating functions
- Partitions
- The Ferrer diagram
- The principle of inclusion and exclusion: derangements
- Polya’s theorem
- The Möbius inversion theorem
- Special problems
  - The Ising problem
  - Self-avoiding random walk
Problems of choice
- Systems of distinct representatives
- Ramsey’s numbers
Design theory
- BIB (balanced incomplete block) designs
- PBIB (partially balanced incomplete block) designs
Latin squares and the packing problem
- Orthogonal Latin squares
- Orthogonal arrays and the packing problem
Graph theory
- Definitions
- Enumeration of graphs
- Characterization problems of graph theory
Applications of graph theory
- Planar graphs
- The four-colour map problem
- Eulerian cycles and the Königsberg bridge problem
- Directed graphs
Combinatorial geometry
- Some historically important topics of combinatorial geometry
  - Packing and covering
  - Polytopes
  - Incidence problems
  - Helly’s theorem
- Methods of combinatorial geometry
  - Exhausting the possibilities
  - Use of extremal properties
  - Use of transformations between different spaces and applications of Helly’s theorem

References & Edit History Quick Facts & Related Topics

Images

Ferrers' partitioning diagram for 14

orthogonal Latin squares

two isomorphic graphs and a tree

two homeomorphic graphs A and B

two graphs important to planar properties

seven bridges of Königsberg and multigraph.

packing of disks

covering of part of a plane with triangles

prism and truncated pyramid

example of theorem on extremal properties

For Students

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combinatorics summary

combinatorics: Facts & Related Content

Written and fact-checked by The Information Architects of Encyclopaedia Britannica

Facts

Also Known As	combinatorial mathematics

Photos

Ferrers' partitioning diagram for 14

orthogonal Latin squares

two isomorphic graphs and a tree

two homeomorphic graphs A and B

two graphs important to planar properties

seven bridges of Königsberg and multigraph.

packing of disks

covering of part of a plane with triangles

prism and truncated pyramid

example of theorem on extremal properties

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Topics

Latin square orthogonal array Euler’s theorem on polyhedrons combination recurrence relation network theory Hall’s theorem König’s theorem Möbius inversion theorem design analysis probability theory cryptology computer science algebra statistics geometry automata theory set theory information theory

Key People

Paul Erdős

Paul Erdős

Hungarian mathematician

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Andrei Okounkov

Russian mathematician

Equations written on blackboard

Numbers and Mathematics