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!)
 A304981 Number of unlabeled clutters (connected antichains) spanning up to n vertices without singleton edges. 7
 1, 1, 2, 5, 19, 176, 16118, 489996568 (list; graph; refs; listen; history; text; internal format)
 OFFSET 0,3 LINKS FORMULA Partial sums of A261006(n > 0). EXAMPLE Non-isomorphic representatives of the a(3) = 5 clutters:   {}   {{1,2}}   {{1,2,3}}   {{1,3},{2,3}}   {{1,2},{1,3},{2,3}} Non-isomorphic representatives of the a(4) = 19 clutters:   {}   {{1,2}}   {{1,2,3}}   {{1,2,3,4}}   {{1,3},{2,3}}   {{1,4},{2,3,4}}   {{1,3,4},{2,3,4}}   {{1,2},{1,3},{2,3}}   {{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. A048143, A198085, A261006, A304912, A304981, A304982, A304983, A304984, A304985, A304986. Sequence in context: A332653 A198203 A014466 * A284860 A108799 A193674 Adjacent sequences:  A304978 A304979 A304980 * A304982 A304983 A304984 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 June 4 09:42 EDT 2020. Contains 334825 sequences. (Running on oeis4.)