%I A002214 M1750 N0694
%S A002214 1,1,2,7,18,64,226,856,3306,13249,53794,222717,933438,3960487,16970362,
%T A002214 73381453,319817670,1403875491,6202064928,27559699507,123115236582,
%U A002214 552654175124,2491870281372,11281732737898,51270697159708
%N A002214 Number of unrooted hexagonal polyominoes with n cells and no reflections 
               allowed.
%D A002214 F. Harary and R. C. Read, The enumeration of tree-like polyhexes, Proc. 
               Edinb. Math. Soc. (2) 17 (1970), 1-13.
%D A002214 N. J. A. Sloane, A Handbook of Integer Sequences, Academic Press, 1973 
               (includes this sequence).
%D A002214 N. J. A. Sloane and Simon Plouffe, The Encyclopedia of Integer Sequences, 
               Academic Press, 1995 (includes this sequence).
%H A002214 T. D. Noe, <a href="b002214.txt">Table of n, a(n) for n=1..200</a>
%F A002214 G.f.=x+xU(x)+(1/2)(3x-1)U(x)^2+(1/2)(1+x)U(x^2)+(1/3)xU(x)^3+(2/3)xU(x^3), 
               where U(x)=[1-3x-sqrt(1-6x+5x^2)]/(2x). - Emeric Deutsch (deutsch(AT)duke.poly.edu), 
               May 02 2004
%Y A002214 Sequence in context: A046672 A046866 A000988 this_sequence A100408 A140562 
               A140550
%Y A002214 Adjacent sequences: A002211 A002212 A002213 this_sequence A002215 A002216 
               A002217
%K A002214 nonn
%O A002214 1,3
%A A002214 N. J. A. Sloane (njas(AT)research.att.com).
%E A002214 More terms from Emeric Deutsch (deutsch(AT)duke.poly.edu), May 02 2004