A376694 Number of permutations of order n avoiding consecutive pattern 121'3.

1, 1, 2, 6, 22, 100, 548, 3482, 25256, 206298, 1871704, 18676354, 203323724, 2397969518, 30455963576, 414446765490, 6015821216380, 92778775395190, 1515047281161392, 26114701159308242, 473827422862284740, 9027024454944900390, 180165845677134636856, 3759286756628732868754, 81850596163629861103004

Offset

0,3

Comments

To avoid 121'3 means not to have four consecutive letters such that the first letter and the third one is less than the second, and the second one is less than and the fourth one.

Links

Table of n, a(n) for n=0..24.

S. Kitaev, Introduction to partially ordered patterns, Discrete Applied Mathematics 155 (2007), 929-944. [WARNING: The sequence is erroneously given as 1, 2, 6, 20, 83, 411, ...]

Crossrefs

Cf. A117156, A177470, A177471, A177472, A177473, A177475, A177476, A177477, A177478, A177479, A177480, A177481, A177482, A177483, A177484.

Sequence in context: A009468 A088819 A177478 * A052517 A245119 A012270

Adjacent sequences: A376691 A376692 A376693 * A376695 A376696 A376697

Keyword

nonn

Author

Max Alekseyev, Oct 01 2024

Status

approved