OFFSET
1,5
REFERENCES
R. W. Robinson, personal communication.
R. W. Robinson, Numerical implementation of graph counting algorithms, AGRC Grant, Math. Dept., Univ. Newcastle, Australia, 1980.
N. J. A. Sloane and Simon Plouffe, The Encyclopedia of Integer Sequences, Academic Press, 1995 (includes this sequence).
LINKS
R. W. Robinson, Table of n, a(n) for n = 1..190
Phil Hanlon, Counting interval graphs, Trans. Amer. Math. Soc. 272 (1982), no. 2, 383-426.
FORMULA
G.f.: -z + (1/4)*(1+2z-z^2)/sqrt((1+z^2)*(1-3z^2)) - (1/4)*sqrt((1-3z)/(1+z)). - Emeric Deutsch, Nov 19 2004
MAPLE
G:=-z+(1+2*z-z^2)/4/sqrt((1+z^2)*(1-3*z^2))-sqrt((1-3*z)/(1+z))/4: Gser:=series(G, z=0, 30): seq(coeff(Gser, z^n), n=1..28); # Emeric Deutsch, Nov 19 2004
CROSSREFS
KEYWORD
nonn
AUTHOR
EXTENSIONS
More terms from Emeric Deutsch, Nov 19 2004
STATUS
approved