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A170934 a(n) = b(n) + b(n+1) + 2, where b() = A000930().

%I A170934 #19 Jul 10 2020 14:10:43
%S A170934 4,4,5,7,9,12,17,24,34,49,71,103,150,219,320,468,685,1003,1469,2152,
%T A170934 3153,4620,6770,9921,14539,21307,31226,45763,67068,98292,144053,
%U A170934 211119,309409,453460,664577,973984,1427442,2092017,3065999,4493439,6585454,9651451
%N A170934 a(n) = b(n) + b(n+1) + 2, where b() = A000930().
%H A170934 G. C. Greubel, <a href="/A170934/b170934.txt">Table of n, a(n) for n = 0..1000</a>
%H A170934 Z. Skupien, <a href="http://dx.doi.org/10.1016/j.disc.2008.11.003">Sparse Hamiltonian 2-decompositions together with exact count of numerous Hamiltonian cycles</a>, Discr. Math., 309 (2009), 6382-6390.
%H A170934 <a href="/index/Rec#order_04">Index entries for linear recurrences with constant coefficients</a>, signature (2,-1,1,-1).
%F A170934 From _Colin Barker_, Jul 25 2013: (Start)
%F A170934 a(n) = 2*a(n-1)-a(n-2)+a(n-3)-a(n-4).
%F A170934 G.f.: -(3*x^3-x^2+4*x-4) / ((x-1)*(x^3+x-1)). (End)
%F A170934 a(n) = a(n-1) + a(n-3) - 2, for n > 2. - _Greg Dresden_, Feb 09 2020
%t A170934 CoefficientList[Series[-(3*x^3 - x^2 + 4*x - 4)/((x - 1)*(x^3 + x - 1)), {x, 0, 50}], x] (* _G. C. Greubel_, Apr 26 2017 *)
%t A170934 LinearRecurrence[{2,-1,1,-1},{4,4,5,7},50] (* _Harvey P. Dale_, Jul 10 2020 *)
%o A170934 (PARI) x='x+O('x^50); Vec(-(3*x^3 - x^2 + 4*x - 4)/((x - 1)*(x^3 + x - 1))) \\ _G. C. Greubel_, Apr 26 2017
%K A170934 nonn,easy
%O A170934 0,1
%A A170934 _N. J. A. Sloane_, Feb 10 2010
%E A170934 More terms from _Colin Barker_, Jul 25 2013