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!)
 A304998 Number of unlabeled antichains of finite sets spanning n vertices without singletons. 19
 1, 0, 1, 3, 15, 160, 15963, 489980652 (list; graph; refs; listen; history; text; internal format)
 OFFSET 0,4 LINKS FORMULA a(n > 0) = A261005(n) - A261005(n - 1). EXAMPLE Non-isomorphic representatives of the a(4) = 15 antichains:   {{1,2,3,4}}   {{1,2},{3,4}}   {{1,4},{2,3,4}}   {{1,3,4},{2,3,4}}   {{1,2},{1,3,4},{2,3,4}}   {{1,3},{1,4},{2,3,4}}   {{1,3},{2,4},{3,4}}   {{1,4},{2,4},{3,4}}   {{1,2,4},{1,3,4},{2,3,4}}   {{1,2},{1,3},{1,4},{2,3,4}}   {{1,2},{1,3},{2,4},{3,4}}   {{1,4},{2,3},{2,4},{3,4}}   {{1,2,3},{1,2,4},{1,3,4},{2,3,4}}   {{1,3},{1,4},{2,3},{2,4},{3,4}}   {{1,2},{1,3},{1,4},{2,3},{2,4},{3,4}} CROSSREFS Cf. A006126, A261005, A304996, A304997, A304998, A304999, A305000, A305001. Sequence in context: A102556 A016065 A005016 * A105611 A329557 A108975 Adjacent sequences:  A304995 A304996 A304997 * A304999 A305000 A305001 KEYWORD nonn AUTHOR Gus Wiseman, May 23 2018 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 May 14 12:37 EDT 2021. Contains 343884 sequences. (Running on oeis4.)