%I M0772 N0295
%S 1,1,2,3,6,10,20,36,72,137,274,543,1086,2219,4438,9285,18570,39587,
%T 79174,171369,342738,751236,1502472,3328218,6656436,14878455,29756910,
%U 67030785,134061570,304036170,608072340,1387247580,2774495160
%N Number of polyhexes with n hexagons, having reflectional symmetry (see Harary and Read for precise definition).
%D J. Brunvoll, S. J. Cyvin and B. N. Cyvin, Isomer enumeration of polygonal systems..., J. Molec. Struct. (Theochem), 364 (1996), 113. (See Table 10.)
%D F. Harary and R. C. Read, The enumeration of treelike polyhexes, Proc. Edinb. Math. Soc. (2) 17 (1970), 113.
%D N. J. A. Sloane, A Handbook of Integer Sequences, Academic Press, 1973 (includes this sequence).
%D N. J. A. Sloane and Simon Plouffe, The Encyclopedia of Integer Sequences, Academic Press, 1995 (includes this sequence).
%H T. D. Noe, <a href="/A002215/b002215.txt">Table of n, a(n) for n=1..200</a>
%F G.f. = z+(1+2z)U(z^2) where U(z)=[13zsqrt(16z+5z^2)]/(2z) (eq. (16) in the HararyRead paper). a(2n)=A002212(n), n>=1; a(2n+1)=2*A002212(n), n>=1.  _Emeric Deutsch_, Mar 14 2004
%Y Cf. A002212.
%K nonn
%O 1,3
%A _N. J. A. Sloane_.
%E More terms from _Emeric Deutsch_, Mar 14 2004
