cp's OEIS Frontend

This is a front-end for the Online Encyclopedia of Integer Sequences, made by Christian Perfect. The idea is to provide OEIS entries in non-ancient HTML, and then to think about how they're presented visually. The source code is on GitHub.

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A123555 Number of standard Young tableaux of type (n+1,n,n-1).

Original entry on oeis.org

0, 2, 16, 168, 2112, 30030, 466752, 7759752, 135980416, 2485891980, 47052314400, 916847954880, 18311313000960, 373542610526280, 7761573156274560, 163893933165976200, 3510476121410184960, 76151734612882397700, 1670824967127762045600, 37036620104665392010800, 828632324276985756528000
Offset: 0

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Author

Amitai Regev (amitai.regev(AT)weizmann.ac.il), Nov 15 2006

Keywords

Comments

For n > 0, a(n) is the number of up-down permutations of length 2n + 1 with no four-term increasing subsequence. Equivalently, this is the number of up-down permutations of length 2n + 1 with no four-term decreasing subsequence; the number of down-up permutations of length 2n + 1 with no four-term increasing subsequence; and the number of down-up permutations of length 2n + 1 with no four-term decreasing subsequence. (An up-down permutation is one whose descent set is {2, 4, 6, ...}.). - Joel B. Lewis, Oct 05 2009

References

  • For definition see James and Kerber, Representation Theory of Symmetric Group, Addison-Wesley, 1981, p. 107.

Crossrefs

Cf. A011553.
For up-down permutations of even length, see A005789. [Joel B. Lewis, Oct 05 2009]

Programs

  • Mathematica
    f[n_]:=16 (3 n)!/((n-1)! (n+1)! (n+3)!)
    (* first do *) Needs["DiscreteMath`Combinatorica`"] (* then *) Table[ NumberOfTableaux@ {n + 1, n, n - 1}, {n, 0, 17}] (* Robert G. Wilson v *)
  • PARI
    for(n=0,25, print1(16*(3*n)!/((n-1)!*(n+1)!*(n+3)!), ", ")) \\ G. C. Greubel, Oct 15 2017

Formula

a(n) = 16*(3*n)!/((n-1)!*(n+1)!*(n+3)!).
(n-1)*(n+3)*(n+1)*a(n) -3*n*(3*n-1)*(3*n-2)*a(n-1)=0, n>1. - R. J. Mathar, Aug 10 2015
G.f.: 2x*3F2(5/3,4/3,2;3,5;27x). - R. J. Mathar, Aug 10 2015
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