The OEIS Foundation is supported by donations from users of the OEIS and by a grant from the Simons Foundation.

 Hints (Greetings from The On-Line Encyclopedia of Integer Sequences!)
 A320446 Covers of triangles by tetrahedra: number of labeled 4-uniform hypergraphs spanning n vertices such that every three vertices appear together in some edge. 0
 1, 1, 1, 0, 1, 6, 5789 (list; graph; refs; listen; history; text; internal format)
 OFFSET 0,6 LINKS EXAMPLE The a(5) = 6 hypergraphs:   {{1234},{1235},{1245},{1345}}   {{1234},{1235},{1245},{2345}}   {{1234},{1235},{1345},{2345}}   {{1234},{1245},{1345},{2345}}   {{1235},{1245},{1345},{2345}}   {{1234},{1235},{1245},{1345},{2345}} MATHEMATICA Table[Length[Select[Subsets[Subsets[Range[n], {4}]], Length[Union@@(Subsets[#, {3}]&/@#)]==Binomial[n, 3]&]], {n, 6}] CROSSREFS Cf. A006126, A038041, A299471, A301922, A302374, A302394, A306021, A319540, A320395, A322451. Sequence in context: A116117 A116135 A011788 * A172649 A111152 A202969 Adjacent sequences:  A320443 A320444 A320445 * A320447 A320448 A320449 KEYWORD nonn,more AUTHOR Gus Wiseman, Jan 10 2019 STATUS approved

Lookup | Welcome | Wiki | Register | Music | Plot 2 | Demos | Index | Browse | More | WebCam
Contribute new seq. or comment | Format | Style Sheet | Transforms | Superseeker | Recent
The OEIS Community | Maintained by The OEIS Foundation Inc.

Last modified January 24 07:18 EST 2020. Contains 331189 sequences. (Running on oeis4.)