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  2. Permutation - Wikipedia

    en.wikipedia.org/wiki/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 positions of the zeroes in the Lehmer code are the positions of the right-to-left minima (in the example positions the 4, 8, 9 of the values 1, 2, 5); this allows computing the distribution ...

  3. Derangement - Wikipedia

    en.wikipedia.org/wiki/Derangement

    In every other permutation of this 4-member set, at least one student gets their own test back (shown in bold red). Another version of the problem arises when we ask for the number of ways n letters, each addressed to a different person, can be placed in n pre-addressed envelopes so that no letter appears in the correctly addressed envelope.

  4. Lehmer code - Wikipedia

    en.wikipedia.org/wiki/Lehmer_code

    Concretely a Lehmer code for the permutation B,F,A,G,D,E,C of letters, ordered alphabetically, would first give the list of sequence numbers 1,5,0,6,3,4,2, which is successively transformed

  5. Permutation group - Wikipedia

    en.wikipedia.org/wiki/Permutation_group

    A permutation group is a subgroup of a symmetric group; that is, its elements are permutations of a given set. It is thus a subset of a symmetric group that is closed under composition of permutations, contains the identity permutation, and contains the inverse permutation of each of its elements. [2]

  6. Automorphisms of the symmetric and alternating groups

    en.wikipedia.org/wiki/Automorphisms_of_the...

    the product of two 2-cycles such as (1 2)(3 4) maps to another product of two 2-cycles such as (3 5)(4 6), accounting for 45 permutations; the product of a 2-cycle and a 4-cycle such as (1 2 3 4)(5 6) maps to another such permutation such as (1 4 2 6)(3 5), accounting for the 90 remaining permutations. And the odd part is also conserved: a 2 ...

  7. Alternating group - Wikipedia

    en.wikipedia.org/wiki/Alternating_group

    Compound of five tetrahedra. A 5 acts on the dodecahedron by permuting the 5 inscribed tetrahedra. Even permutations of these tetrahedra are exactly the symmetric rotations of the dodecahedron and characterizes the A 5 < SO 3 (R) correspondence. A 5 is the group of isometries of a dodecahedron in 3-space, so there is a representation A 5 → SO ...

  8. Breaking the Filibuster

    data.huffingtonpost.com/2012/12/filibuster-reform

    HuffPost is tracking where Democratic senators stand on filibuster reform.

  9. Permutation codes - Wikipedia

    en.wikipedia.org/wiki/Permutation_Codes

    A main problem in permutation codes is to determine the value of (,), where (,) is defined to be the maximum number of codewords in a permutation code of length and minimum distance . There has been little progress made for 4 ≤ d ≤ n − 1 {\displaystyle 4\leq d\leq n-1} , except for small lengths.