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  2. Sum coloring - Wikipedia

    en.wikipedia.org/wiki/Sum_coloring

    The sum of the labels is 11, smaller than could be achieved using only two labels. In graph theory, a sum coloring of a graph is a labeling of its vertices by positive integers, with no two adjacent vertices having equal labels, that minimizes the sum of the labels. The minimum sum that can be achieved is called the chromatic sum of the graph. [1]

  3. Graph coloring - Wikipedia

    en.wikipedia.org/wiki/Graph_coloring

    Sum of the distance between the vertices and the difference of their colors is greater than k + 1, where k is a positive integer. Rank coloring If two vertices have the same color i, then every path between them contain a vertex with color greater than i Subcoloring An improper vertex coloring where every color class induces a union of cliques

  4. List of reagent testing color charts - Wikipedia

    en.wikipedia.org/wiki/List_of_reagent_testing...

    It is advised to check the references for photos of reaction results. [1] Reagent testers might show the colour of the desired substance while not showing a different colour for a more dangerous additive. [2]

  5. Chromatic polynomial - Wikipedia

    en.wikipedia.org/wiki/Chromatic_polynomial

    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.

  6. CIE 1931 color space - Wikipedia

    en.wikipedia.org/wiki/CIE_1931_color_space

    The color matching functions are proportional to the intensities of primaries needed to match the monochromatic test color at the wavelength shown on the horizontal scale. In 1931 the International Commission on Illumination (CIE) published the CIE 1931 color spaces which define the relationship between the visible spectrum and human color vision.

  7. Van der Waerden's theorem - Wikipedia

    en.wikipedia.org/wiki/Van_der_Waerden's_theorem

    Van der Waerden's theorem is a theorem in the branch of mathematics called Ramsey theory.Van der Waerden's theorem states that for any given positive integers r and k, there is some number N such that if the integers {1, 2, ..., N} are colored, each with one of r different colors, then there are at least k integers in arithmetic progression whose elements are of the same color.

  8. Ramanujan's sum - Wikipedia

    en.wikipedia.org/wiki/Ramanujan's_sum

    In number theory, Ramanujan's sum, usually denoted c q (n), is a function of two positive integer variables q and n defined by the formula c q ( n ) = ∑ 1 ≤ a ≤ q ( a , q ) = 1 e 2 π i a q n , {\displaystyle c_{q}(n)=\sum _{1\leq a\leq q \atop (a,q)=1}e^{2\pi i{\tfrac {a}{q}}n},}

  9. Color difference - Wikipedia

    en.wikipedia.org/wiki/Color_difference

    As most definitions of color difference are distances within a color space, the standard means of determining distances is the Euclidean distance.If one presently has an RGB (red, green, blue) tuple and wishes to find the color difference, computationally one of the easiest is to consider R, G, B linear dimensions defining the color space.