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.

A059375 Number of seating arrangements for the ménage problem.

Original entry on oeis.org

1, 0, 0, 12, 96, 3120, 115200, 5836320, 382072320, 31488549120, 3191834419200, 390445460697600, 56729732529254400, 9659308746908620800, 1905270127543015833600, 431026303509734220288000, 110865322076320374571008000, 32172949121885378686623744000
Offset: 0

Views

Author

N. J. A. Sloane, Jan 28 2001

Keywords

Comments

The "probleme des menages" asks for the number of gender-alternating seating arrangements for n couples around a circular table with the condition that no two spouses are seated adjacently. - Paul C. Kainen and Michael Somos, Mar 11 2011

Examples

			a(3) = 12 because there is a unique seating arrangement up to circular and clockwise / counterclockwise symmetry. - _Paul C. Kainen_ and _Michael Somos_, Mar 11 2011
		

References

  • L. Comtet, Advanced Combinatorics, Reidel, 1974, p. 184, mu*(n).
  • H. J. Ryser, Combinatorial Mathematics. Mathematical Association of America, Carus Mathematical Monograph 14, 1963, p. 32. equation (2.3).

Crossrefs

Programs

  • Mathematica
    a[0] = 1; a[1] = 0; a[n_] := 4n n! Sum[(-1)^k Binomial[2n-k, k] (n-k)! / (2n-k), {k, 0, n}]; Table[a[n], {n, 0, 17}] (* Jean-François Alcover, Jun 19 2017, from 1st formula *)
  • PARI
    {a(n) = local(A); if( n<3, n==0, A = vector(n); A[3] = 1; for(k=4, n, A[k] = (k * (k - 2) * A[k-1] + k * A[k-2] - 4 * (-1)^k) / (k-2)); 2 * n! * A[n])} /* Michael Somos, Mar 11 2011 */

Formula

a(n) = A000179(n) * 2 * n!.
a(n) = A094047(n) * 2 * n.