OFFSET
1,3
LINKS
P. J. Cameron, Some treelike objects, Quart. J. Math. Oxford, 38 (1987), 155-183. See p. 166.
Jacinta Covington, A universal structure for N-free graphs, Proc. London Math. Soc. (3) 58 (1989), no. 1, 1--16. MR0969544 (89m:03028).
FORMULA
a(1)=1, thereafter a(n) = A226909(n)/2.
CROSSREFS
KEYWORD
nonn
AUTHOR
N. J. A. Sloane, Apr 18 2014
STATUS
approved