OFFSET
2,3
COMMENTS
Also the number of unlabeled cographs on n nodes with two components. - Vladeta Jovovic, May 07 2005
REFERENCES
J. Riordan, The blossoming of Schroeder's fourth problem, Acta Math., 137 (1976), 1-16.
LINKS
Eric Weisstein's World of Mathematics, Cograph
FORMULA
G.f.: A(x) = (B(x)^2 + B(x^2))/2, where B(x) = g.f. for A000669. - Vladeta Jovovic, May 07 2005
CROSSREFS
KEYWORD
nonn
AUTHOR
N. J. A. Sloane, Jan 01 2001
EXTENSIONS
More terms from Vladeta Jovovic, May 07 2005
STATUS
approved