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%I #35 Sep 08 2022 08:45:55
%S 23,141,652,2735,11168,44975,180508,722823,2893168,11575127,46307132,
%T 185237279,740974336,2963930847,11855822524,47423422103,189694082672,
%U 758776856135,3035108998684,12140438093295,48561758666176,194247043054991
%N a(n) = floor((265/6)*4^(n-4) - n^2 - ((15+(-1)^(n-1))/6)* 2^(n-3)).
%C An upper bound on the crossing number of the locally twisted n-dimensional hypercube LTQ(n). From Wang, p. 3. A lower bound is given in A188162 (may not be meaningful for n<4).
%H Vincenzo Librandi, <a href="/A185098/b185098.txt">Table of n, a(n) for n = 4..1000</a>
%H Haoli Wang, Xirong Xu, Yuansheng Yang, Bao Liu, Wenping Zheng and Guoqing Wang, <a href="http://arxiv.org/abs/1103.4227">The crossing number of locally twisted cubes</a>, arXiv:1103.4227 [math.CO], Mar 22, 2011.
%F Empirical G.f.: -x^4*(8*x^6-36*x^5+22*x^4+67*x^3-82*x^2-20*x+23) / ((x-1)^3*(2*x-1)*(2*x+1)*(4*x-1)). - _Colin Barker_, Dec 04 2012
%e a(4) = floor(((265 / 6) * (4^(4 - 4))) - ((4^2) + (((15 + ((-1)^(4 - 1))) / 6) * (2^(4 - 3))))) = floor(23.5) = 23.
%e a(5) = floor(((265 / 6) * (4^(5 - 4))) - ((5^2) + (((15 + ((-1)^(5 - 1))) / 6) * (2^(5 - 3))))) = floor(141) = 141.
%t Table[Floor[(265/6)*4^(n-4) - n^2 - ((15+(-1)^(n-1))/6)* 2^(n-3)], {n,4,50}] (* _G. C. Greubel_, Jun 22 2017 *)
%o (PARI) a(n)=floor((265/6)*(4^(n-4))-(n^2 + ((15+(-1)^(n-1))/6)*(2^(n-3))))
%o (Magma) [Floor((265/6)*(4^(n-4))-(n^2 + ((15+(-1)^(n-1))/6)*(2^(n-3)))): n in [4..30]]; // _Vincenzo Librandi_, Mar 25 2012
%Y Cf. A188162.
%K nonn,easy
%O 4,1
%A _Jonathan Vos Post_, Mar 23 2011
%E More terms from _Franklin T. Adams-Watters_, Mar 24 2011
%E More terms from _Sean A. Irvine_, May 24 2011
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