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%I #19 Feb 25 2020 08:14:01
%S 1,2,10,42,182,790,3432,14914,64814,281680,1224182,5320310,23122148,
%T 100489226,436727814,1898026232,8248853134,35849651070,155803171860,
%U 677123141810,2942788286798,12789406189672,55582969192486,241564496305670,1049843265359828
%N Number of tilings of a 4 X 2n rectangle with L tetrominoes.
%H Colin Barker, <a href="/A084480/b084480.txt">Table of n, a(n) for n = 0..1000</a>
%H C. Moore, <a href="http://arXiv.org/abs/math.CO/9905012">[math/9905012] Some Polyomino Tilings of the Plane</a>
%H <a href="/index/Rec#order_06">Index entries for linear recurrences with constant coefficients</a>, signature (4,2,-1,-4,-4,-2).
%F G.f.: (1-2*z-z^3) / (1-4*z-2*z^2+z^3+4*z^4+4*z^5+2*z^6).
%F a(n) = 4*a(n-1) + 2*a(n-2) - a(n-3) - 4*a(n-4) - 4*a(n-5) - 2*a(n-6) for n>5. - _Colin Barker_, Mar 28 2017
%t LinearRecurrence[{4, 2, -1, -4, -4, -2}, {1, 2, 10, 42, 182, 790}, 25] (* _Jean-François Alcover_, Feb 25 2020 *)
%o (PARI) Vec((1 - 2*x - x^3) / (1 - 4*x - 2*x^2 + x^3 + 4*x^4 + 4*x^5 + 2*x^6) + O(x^30)) \\ _Colin Barker_, Mar 28 2017
%Y Cf. A084478, A084479, A084477, A084481, A174248, A226322, A232497.
%K nonn,easy
%O 0,2
%A _Ralf Stephan_, May 27 2003
%E Inserted a(0)=1 by _Alois P. Heinz_, May 01 2013
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