A141473 Number of 3-equitable permutations: permutations on n letters equally avoiding each permutation of S_3.

6, 2, 2, 0, 0, 4, 2, 0, 0

Offset: 3

Author

Sunil Abraham (sunil.abraham(AT)lmh.ox.ac.uk), Aug 08 2008

Keywords

• nonn
• hard
• more

Comments

A permutation is 3-equitable if no omega in S_3 appears more than ceiling(binomial(n,3)/6) times or fewer than floor(binomial(n,3)/6) times.

E.g., 2143 contains 214, 213--213 permutations--and 243 and 143--both 132 permutations.

This is a generalization of the Kendall-Mann numbers A000140.

Examples

			The only 3-equitable permutations in S_4: [3, 1, 4, 2], [2, 4, 1, 3].
		

Links

• Sunil Abraham, Maple program

Crossrefs

Cf. A000140.