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  2. Permutation - Wikipedia

    en.wikipedia.org/wiki/Permutation

    The sum of the numbers in the factorial number system representation gives the number of inversions of the permutation, and the parity of that sum gives the signature of the permutation. Moreover, the positions of the zeroes in the inversion table give the values of left-to-right maxima of the permutation (in the example 6, 8, 9) while the ...

  3. Catalan number - Wikipedia

    en.wikipedia.org/wiki/Catalan_number

    C n is the number of standard Young tableaux whose diagram is a 2-by-n rectangle. In other words, it is the number of ways the numbers 1, 2, ..., 2n can be arranged in a 2-by-n rectangle so that each row and each column is increasing. As such, the formula can be derived as a special case of the hook-length formula.

  4. Lehmer code - Wikipedia

    en.wikipedia.org/wiki/Lehmer_code

    The usual way to prove that there are n! different permutations of n objects is to observe that the first object can be chosen in n different ways, the next object in n − 1 different ways (because choosing the same number as the first is forbidden), the next in n − 2 different ways (because there are now 2 forbidden values), and so forth.

  5. Levi-Civita symbol - Wikipedia

    en.wikipedia.org/wiki/Levi-Civita_symbol

    The formula is valid for all index values, and for any n (when n = 0 or n = 1, this is the empty product). However, computing the formula above naively has a time complexity of O(n 2), whereas the sign can be computed from the parity of the permutation from its disjoint cycles in only O(n log(n)) cost.

  6. Landau's function - Wikipedia

    en.wikipedia.org/wiki/Landau's_function

    In mathematics, Landau's function g(n), named after Edmund Landau, is defined for every natural number n to be the largest order of an element of the symmetric group S n. Equivalently, g ( n ) is the largest least common multiple (lcm) of any partition of n , or the maximum number of times a permutation of n elements can be recursively applied ...

  7. Parity of a permutation - Wikipedia

    en.wikipedia.org/wiki/Parity_of_a_permutation

    The numbers in the right column are the inversion numbers (sequence A034968 in the OEIS), which have the same parity as the permutation. In mathematics, when X is a finite set with at least two elements, the permutations of X (i.e. the bijective functions from X to X) fall into two classes of equal size: the even permutations and the odd ...

  8. Integer partition - Wikipedia

    en.wikipedia.org/wiki/Integer_partition

    and the number of partitions of n in which all parts are 1, 2 or 3 (or, equivalently, the number of partitions of n into at most three parts) is the nearest integer to (n + 3) 2 / 12. [ 14 ] Partitions in a rectangle and Gaussian binomial coefficients

  9. Transposable integer - Wikipedia

    en.wikipedia.org/wiki/Transposable_integer

    For any integer coprime to 10, its reciprocal is a repeating decimal without any non-recurring digits. E.g. 1 ⁄ 143 = 0. 006993 006993 006993.... While the expression of a single series with vinculum on top is adequate, the intention of the above expression is to show that the six cyclic permutations of 006993 can be obtained from this repeating decimal if we select six consecutive digits ...