

A275307


Number of labeled spanning blobs on n vertices.


38




OFFSET

1,3


COMMENTS

A clutter is a set of sets comprising a connected antichain in the Boolean algebra B_n. A blob is defined as a clutter that cannot be capped by a tree.


LINKS



FORMULA

Every clutter is a tree of blobs, so we have A048143(n) = Sum_p n^(k1) Prod_i a(p_i+1), where the sum is over all set partitions U(p_1,...,p_k) = {1,...,n1}.


EXAMPLE

The a(3)=2 blobs are: {{1,2,3}}, {{1,2},{1,3},{2,3}}.


CROSSREFS



KEYWORD

nonn,more


AUTHOR



STATUS

approved



