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A261005 Number of unlabeled simplicial complexes with n nodes. 34
1, 1, 2, 5, 20, 180, 16143, 489996795 (list; graph; refs; listen; history; text; internal format)
OFFSET

0,3

COMMENTS

Also the number of non-isomorphic antichains of nonempty sets covering n vertices. The labeled case is A006126, except with a(0) = 1. - Gus Wiseman, Feb 23 2019

REFERENCES

BenoƮt Jubin, Posting to Sequence Fans Mailing List, Aug 12 2015

C Lienkaemper, A Shiu, Z Woodstock, Obstructions to convexity in neural codes, Preprint 2015; http://www.math.tamu.edu/~annejls/papers/obstructions-convexity-neural.pdf

LINKS

Table of n, a(n) for n=0..7.

Gus Wiseman, Sequences enumerating clutters, antichains, hypertrees, and hyperforests, organized by labeling, spanning, and allowance of singletons.

FORMULA

First differences of A306505. - Gus Wiseman, Feb 23 2019

EXAMPLE

From Gus Wiseman, Feb 23 2019: (Start)

Non-isomorphic representatives of the a(0) = 1 through a(4) = 20 antichains:

  {}  {{1}}  {{12}}    {{123}}         {{1234}}

             {{1}{2}}  {{1}{23}}       {{1}{234}}

                       {{13}{23}}      {{12}{34}}

                       {{1}{2}{3}}     {{14}{234}}

                       {{12}{13}{23}}  {{1}{2}{34}}

                                       {{134}{234}}

                                       {{1}{24}{34}}

                                       {{1}{2}{3}{4}}

                                       {{13}{24}{34}}

                                       {{14}{24}{34}}

                                       {{13}{14}{234}}

                                       {{12}{134}{234}}

                                       {{1}{23}{24}{34}}

                                       {{124}{134}{234}}

                                       {{12}{13}{24}{34}}

                                       {{14}{23}{24}{34}}

                                       {{12}{13}{14}{234}}

                                       {{123}{124}{134}{234}}

                                       {{13}{14}{23}{24}{34}}

                                       {{12}{13}{14}{23}{24}{34}}

(End)

CROSSREFS

Apart from a(0), same as A006602, and after subtracting 1, A007411.

Cf. A000372, A003182, A006126, A014466, A261006, A304997, A304998, A306505, A306550, A321679.

Sequence in context: A156871 A058109 A005331 * A158872 A308522 A216462

Adjacent sequences:  A261002 A261003 A261004 * A261006 A261007 A261008

KEYWORD

nonn

AUTHOR

N. J. A. Sloane, Aug 13 2015

STATUS

approved

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Last modified March 28 17:51 EDT 2020. Contains 333103 sequences. (Running on oeis4.)