OFFSET
1,3
EXAMPLE
a(1) = 1, a(2) = 1 and a(3) = 2 coincide with the first three terms of A001190, as all connected triangle-free DAGs with at most three vertices are necessarily trees.
For n = 4, the a(4) = 5 solutions are the following three trees:
(((())))
((), (()))
(((), ()))
together with two 4-cycles.
CROSSREFS
KEYWORD
nonn,more
AUTHOR
Adam P. Goucher, Jun 12 2019
STATUS
approved