A293153 Euler number of a certain poset C^bar_n.

12, 150, 3192, 106290

Offset

1,1

Comments

The definitions of Q_n given in Exercise 12 and Open Problem 16 of Morales et al. (2016) seem inconsistent, so the definition of this sequence is not clear to me.

Exercise 12 asks for the number of permutations (a_1,...,a_n,b_1,...b_n) in S_{2n} such that a_i < b_j for all 1 <= i < j <= n. So this must be a different Q_n.

Links

Table of n, a(n) for n=1..4.

Alejandro H. Morales, I. Pak, G. Panova, Why is pi < 2 phi?, Preprint, 2016. See Exercise 12 and Open Problem 16.

Crossrefs

Sequence in context: A053507 A060917 A113358 * A015611 A127650 A286432

Adjacent sequences: A293150 A293151 A293152 * A293154 A293155 A293156

Keyword

nonn,more

Author

N. J. A. Sloane, Oct 09 2017

Status

approved