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%I #16 Dec 20 2019 14:52:50
%S 18,102,418,2006,8946,41222,187202,855606,3899538,17794662,81157858,
%T 370232726,1688782386,7703577542,35140060802,160293673206,731187195858
%N Number of strong restricted edge-subgraphs in Moebius ladder M_n.
%H Sean A. Irvine, <a href="https://github.com/archmageirvine/joeis/blob/master/src/irvine/oeis/a020/A020881.java">Java program</a> (github)
%H J. P. McSorley, <a href="http://dx.doi.org/10.1016/S0012-365X(97)00086-1">Counting structures in the Moebius ladder</a>, Discrete Math., 184 (1998), 137-164.
%F For large n, (3.2143)^n < a(n) < (6.4188)^n (Th. 23.1.) - C. Ronaldo (aga_new_ac(AT)hotmail.com), Jan 17 2005
%F Conjectures from _Colin Barker_, Dec 20 2019: (Start)
%F G.f.: 2*x^2*(9 + 33*x + 8*x^2 - 12*x^3) / ((1 + x)*(1 + 2*x)*(1 - 5*x + 2*x^2)).
%F a(n) = 2*a(n-1) + 11*a(n-2) + 4*a(n-3) - 4*a(n-4) for n>5.
%F (End)
%K nonn,more
%O 2,1
%A _N. J. A. Sloane_.
%E a(6)-a(18) from _Sean A. Irvine_, Apr 30 2019
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