This is a front-end for the Online Encyclopedia of Integer Sequences, made by Christian Perfect. The idea is to provide OEIS entries in non-ancient HTML, and then to think about how they're presented visually. The source code is on GitHub.
%I A002215 M0772 N0295 #23 Oct 14 2023 23:50:16 %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 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="/A002215/b002215.txt">Table of n, a(n) for n = 1..200</a>. %H A002215 J. Brunvoll, S. J. Cyvin, and B. N. Cyvin, <a href="http://dx.doi.org/10.1016/0166-1280(95)04463-9">Isomer enumeration of polygonal systems...</a>, J. Molec. Struct. (Theochem), 364 (1996), 1-13, Table 10. %H A002215 F. Harary and R. C. Read, <a href="https://doi.org/10.1017/S0013091500009135">The enumeration of tree-like polyhexes</a>, Proc. Edinburgh Math. Soc. (2) 17 (1970), 1-13. %F A002215 From _Emeric Deutsch_, Mar 14 2004: (Start) %F A002215 G.f.: z + (1+2*z)*U(z^2) where U(z) = (1 - 3*z - sqrt(1-6*z+5*z^2))/(2*z) (eq. (16) in the Harary-Read paper). %F A002215 a(2n) = A002212(n), n >= 1; a(2n+1) = 2*A002212(n), n >= 1. (End) %Y A002215 Cf. A002212. %K A002215 nonn %O A002215 1,3 %A A002215 _N. J. A. Sloane_ %E A002215 More terms from _Emeric Deutsch_, Mar 14 2004