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The choosability (or list colorability or list chromatic number) ch(G) of a graph G is the least number k such that G is k-choosable. More generally, for a function f assigning a positive integer f(v) to each vertex v, a graph G is f-choosable (or f-list-colorable) if it has a list coloring no matter how one assigns a list of f(v) colors to ...
With four colors, it can be colored in 24 + 4 × 12 = 72 ways: using all four colors, there are 4! = 24 valid colorings (every assignment of four colors to any 4-vertex graph is a proper coloring); and for every choice of three of the four colors, there are 12 valid 3-colorings. So, for the graph in the example, a table of the number of valid ...
3. Grötzsch's theorem that triangle-free planar graphs can always be colored with at most three colors. Grundy number 1. The Grundy number of a graph is the maximum number of colors produced by a greedy coloring, with a badly-chosen vertex ordering.
We can also generalize the induced Ramsey's theorem to a multicolor setting. For graphs H 1, H 2, …, H r, define r ind (H 1, H 2, …, H r) to be the minimum number of vertices in a graph G such that any coloring of the edges of G into r colors contain an induced subgraph isomorphic to H i where all edges are colored in the i-th color for ...
A synonym for a function between sets or a morphism in a category. Depending on authors, the term "maps" or the term "functions" may be reserved for specific kinds of functions or morphisms (e.g., function as an analytic term and map as a general term). mathematics See mathematics. multivalued
George David Birkhoff introduced the chromatic polynomial in 1912, defining it only for planar graphs, in an attempt to prove the four color theorem.If (,) denotes the number of proper colorings of G with k colors then one could establish the four color theorem by showing (,) > for all planar graphs G.
Days in California schools are numbered for snacks like Flamin’ Hot Cheetos, some cereals, baked goods and other products that contain a number of synthetic food dyes.
The number of aperiodic necklaces (or equivalently Lyndon words), which are cyclic arrangements of n colored beads having α available colors. Two such necklaces are considered equal if they are related by a rotation (not considering reflections). Aperiodic refers to necklaces without rotational symmetry, having n distinct rotations.