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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. 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.

  4. Symmetric mean absolute percentage error - Wikipedia

    en.wikipedia.org/wiki/Symmetric_mean_absolute...

    The absolute difference between A t and F t is divided by half the sum of absolute values of the actual value A t and the forecast value F t. The value of this calculation is summed for every fitted point t and divided again by the number of fitted points n.

  5. Positive element - Wikipedia

    en.wikipedia.org/wiki/Positive_element

    The unit element of an unital *-algebra is positive.; For each element , the elements and are positive by definition. [1]In case is a C*-algebra, the following holds: . Let be a normal element, then for every positive function which is continuous on the spectrum of the continuous functional calculus defines a positive element ().

  6. Glossary of mathematical symbols - Wikipedia

    en.wikipedia.org/wiki/Glossary_of_mathematical...

    Internal direct sum: if E and F are abelian subgroups of an abelian group V, notation = means that V is the direct sum of E and F; that is, every element of V can be written in a unique way as the sum of an element of E and an element of F.

  7. CIE 1931 color space - Wikipedia

    en.wikipedia.org/wiki/CIE_1931_color_space

    An equal, additive mixture of two colors will not generally lie on the midpoint of that line segment, unless the sum of the X, Y, and Z values of one color is equal to the sum of the X, Y, and Z values of the other color (that is, both colors lie in the same X=Y=Z plane).

  8. Summation - Wikipedia

    en.wikipedia.org/wiki/Summation

    In mathematics, summation is the addition of a sequence of numbers, called addends or summands; the result is their sum or total.Beside numbers, other types of values can be summed as well: functions, vectors, matrices, polynomials and, in general, elements of any type of mathematical objects on which an operation denoted "+" is defined.

  9. Summation by parts - Wikipedia

    en.wikipedia.org/wiki/Summation_by_parts

    It may be used to prove Nicomachus's theorem that the sum of the first cubes equals the square of the sum of the first positive integers. [2] Summation by parts is frequently used to prove Abel's theorem and Dirichlet's test.