A367873 Irregular triangle read by rows: T(n,k) = number of permutations of length n avoiding simultaneously the patterns 132 and 321 with the maximum number of non-overlapping ascents equal to k.

1, 1, 1, 0, 4, 0, 4, 3, 0, 0, 11, 0, 0, 9, 7, 0, 0, 0, 22, 0, 0, 0, 16, 13, 0, 0, 0, 0, 37, 0, 0, 0, 0, 25, 21, 0, 0, 0, 0, 0, 56, 0, 0, 0, 0, 0, 36, 31, 0, 0, 0, 0, 0, 0, 79, 0, 0, 0, 0, 0, 0, 49, 43, 0, 0, 0, 0, 0, 0, 0, 106

Offset

0,5

Comments

An ascent in a permutation a(1)a(2)...a(n) is position i such that a(i) < a(i+1).

Links

Table of n, a(n) for n=0..70.

Tian Han and Sergey Kitaev, Joint distributions of statistics over permutations avoiding two patterns of length 3, arXiv:2311.02974 [math.CO], 2023.

Formula

G.f.: (1 + x + x^2 - 2*x^2*y + x^3*y + x^4*y + 3*x^4*y^2 + 2*x^5*y^2)/(1 - x^2*y)^3.

Example

1,
1, 1,
0, 4,
0, 4, 3,
0, 0, 11,
0, 0, 9, 7,
0, 0, 0, 22,
0, 0, 0, 16, 13,
0, 0, 0, 0, 37,
0, 0, 0, 0, 25, 21,
0, 0, 0, 0, 0, 56,
0, 0, 0, 0, 0, 36, 31,
0, 0, 0, 0, 0, 0, 79,
0, 0, 0, 0, 0, 0, 49, 43,
0, 0, 0, 0, 0, 0, 0, 106

Crossrefs

Cf. A367631.

Sequence in context: A135031 A238002 A361618 * A016680 A062524 A152856

Adjacent sequences: A367870 A367871 A367872 * A367874 A367875 A367876

Keyword

nonn,tabf

Author

Tian Han, Dec 03 2023

Status

approved