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

Author

Max Alekseyev, Oct 01 2024

Keywords

• nonn

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

• 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.