%I A002215 M0772 N0295
%S A002215 1,1,2,3,6,10,20,36,72,137,274,543,1086,2219,4438,9285,18570,39587,
%T A002215 79174,171369,342738,751236,1502472,3328218,6656436,14878455,29756910,
%U A002215 67030785,134061570,304036170,608072340,1387247580,2774495160
%N A002215 Number of polyhexes with n hexagons, having reflectional symmetry (see 
               Harary and Read for precise definition).
%D A002215 J. Brunvoll, S. J. Cyvin and B. N. Cyvin, Isomer enumeration of polygonal 
               systems..., J. Molec. Struct. (Theochem), 364 (1996), 1-13. (See 
               Table 10.)
%D A002215 F. Harary and R. C. Read, The enumeration of tree-like polyhexes, Proc. 
               Edinb. Math. Soc. (2) 17 (1970), 1-13.
%D A002215 N. J. A. Sloane, A Handbook of Integer Sequences, Academic Press, 1973 
               (includes this sequence).
%D A002215 N. J. A. Sloane and Simon Plouffe, The Encyclopedia of Integer Sequences, 
               Academic Press, 1995 (includes this sequence).
%H A002215 T. D. Noe, <a href="b002215.txt">Table of n, a(n) for n=1..200</a>
%F A002215 G.f. = z+(1+2z)U(z^2) where U(z)=[1-3z-sqrt(1-6z+5z^2)]/(2z) (eq. (16) 
               in the Harary-Read paper). a(2n)=A002212(n), n>=1; a(2n+1)=2*A002212(n), 
               n>=1. - Emeric Deutsch (deutsch(AT)duke.poly.edu), Mar 14 2004
%Y A002215 Cf. A002212.
%Y A002215 Sequence in context: A006606 A120421 A005418 this_sequence A007562 A008929 
               A066062
%Y A002215 Adjacent sequences: A002212 A002213 A002214 this_sequence A002216 A002217 
               A002218
%K A002215 nonn
%O A002215 1,3
%A A002215 N. J. A. Sloane (njas(AT)research.att.com).
%E A002215 More terms from Emeric Deutsch (deutsch(AT)duke.poly.edu), Mar 14 2004