|
%I #34 Sep 08 2022 08:46:04
%S 23,86,284,856,2416,6496,16832,42368,104192,251392,596992,1398784,
%T 3239936,7430144,16891904,38109184,85393408,190185472,421265408,
%U 928514048,2037383168,4452253696,9693036544,21030240256,45483032576,98079604736,210923159552
%N a(n) = 2^(n-4)*(4*n^2 - 16*n + 23).
%H Vincenzo Librandi, <a href="/A217529/b217529.txt">Table of n, a(n) for n = 4..1000</a>
%H W. Griffiths, R. Smith and D. Warren, <a href="http://www.mat.unisi.it/newsito/puma/public_html/22_2/griffiths_smith_warren.pdf">Almost avoiding pairs of permutations</a>, PU. M. A. Vol. 22 (2011), 129-139.
%H <a href="/index/Rec#order_03">Index entries for linear recurrences with constant coefficients</a>, signature (6,-12,8).
%F From _Colin Barker_, Oct 17 2012: (Start)
%F a(n) = 6*a(n-1) - 12*a(n-2) + 8*a(n-3).
%F G.f.: -x^4*(44*x^2 - 52*x + 23)/(2*x-1)^3. (End)
%t Table[2^(n-4) (4 n^2 - 16 n + 23), {n, 4, 30}] (* _Vincenzo Librandi_, Mar 11 2013 *)
%t LinearRecurrence[{6,-12,8},{23,86,284},30] (* _Harvey P. Dale_, Oct 06 2019 *)
%o (Maxima) makelist(2^(n-4)*(4*n^2-16*n+23), n, 4, 30); /* _Martin Ettl_, Oct 15 2012 */
%o (Magma) [2^(n-4)*(4*n^2-16*n+23): n in [4..30]]; // _Vincenzo Librandi_, Mar 11 2013
%K nonn,easy
%O 4,1
%A _N. J. A. Sloane_, Oct 13 2012
|
