A202061 Number of ascent sequences avoiding the pattern 120.

1, 1, 2, 5, 14, 42, 133, 442, 1535, 5546, 20754, 80113, 317875, 1292648, 5374073, 22794182, 98462847, 432498659, 1929221610, 8728815103, 40017844229, 185727603829, 871897549029, 4137132922197, 19828476952117, 95934298966615, 468291607852143, 2305162065138433

Offset: 0

Author

N. J. A. Sloane, Dec 10 2011

Keywords

• nonn

Comments

It appears that no formula or g.f. is known.

Links

• Liang Chengwei, Shi Lecun and Cai Zhongyu, Table of n, a(n) for n = 0..500 (terms 0..74 from Andrew Conway and Miles Conway)
• Andrew R. Conway, Miles Conway, Andrew Elvey Price and Anthony J. Guttmann, Pattern-avoiding ascent sequences of length 3, arXiv:2111.01279 [math.CO], Nov 01 2021.
• Paul Duncan and Einar Steingrimsson, Pattern avoidance in ascent sequences, arXiv preprint arXiv:1109.3641 [math.CO], 2011.

Crossrefs

Total number of ascent sequences is given by A022493. Number of ascent sequences avoiding 001 (and others) is A000079; 102 is A007051; 101 is A000108; 000 is A202058; 100 is A202059; 110 is A202060; 120 is A202061; 201 is A202062; 210 is A108304; 0123 is A080937; 0021 is A007317.

Extensions

More terms from Anthony Guttmann, Nov 04 2021