A213685 Arises in enumerating maximal antichains of minimum size.

1, 3, 6, 9, 12, 17, 22, 28, 33, 41, 48, 57, 64, 75, 84, 96, 105, 119, 130, 145, 156, 173, 186, 204, 217, 237, 252, 273, 288, 311, 328, 352, 369, 395, 414, 441, 460, 489, 510, 540, 561, 593, 616, 649, 672, 707, 732, 768, 793, 831, 858, 897, 924, 965, 994, 1036

Offset

4,2

Comments

Rightmost column of Table 1: Computational results for small values of n, of Kalinowski.

Links

Table of n, a(n) for n=4..59.

Thomas Kalinowski, Uwe Leck, and Ian T. Roberts, Maximal antichains of minimum size, arXiv:1206.3007v1 [math.CO], Jun 14 2012.

Yaohui Zhu, Kaiming Sun, Zhengdong Luo, and Lingfeng Wang, Progressive Self-Learning for Domain Adaptation on Symbolic Regression of Integer Sequences, Proc. 39th AAAI Conf. Artif. Intel. (2025) Vol. 39, No. 1, 1692-1699. See p. 1698.

Prog

(Python)
[n*(n-1)//2 - (3*n**2+6*n+15 if n%2 else 3*n**2+8*n)//16 for n in range(4, 17)] # Andrei Zabolotskii, Nov 01 2025

Crossrefs

Sequence in context: A127621 A049707 A378763 * A271449 A261956 A344683

Adjacent sequences: A213682 A213683 A213684 * A213686 A213687 A213688

Keyword

easy,nonn

Author

Jonathan Vos Post, Jun 17 2012

Extensions

Keyword "hard" changed to "easy", terms a(17) onwards added using the definition of f(n) on p. 6 of Kalinowski et al. by Andrei Zabolotskii, Nov 01 2025

Status

approved