OFFSET
1,4
EXAMPLE
a(3)=1: the non-edge joins two leaves. a(4)=3: The non-edge joins two leaves of the star graph; or the non-edge joins the two leaves of the linear graph; or the non-edge joins a leaf with the node at distance 2.
CROSSREFS
KEYWORD
nonn
AUTHOR
Brendan McKay, May 05 2018
STATUS
approved