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A217528 a(n) = (n-2)*(n-3)*2^(n-2)+2^n-2. 1

%I

%S 1,2,6,22,78,254,766,2174,5886,15358,38910,96254,233470,557054,

%T 1310718,3047422,7012350,15990782,36175870,81264638,181403646,

%U 402653182,889192446,1954545662,4278190078,9328132094,20266876926,43889197054,94757715966,204010946558

%N a(n) = (n-2)*(n-3)*2^(n-2)+2^n-2.

%H Vincenzo Librandi, <a href="/A217528/b217528.txt">Table of n, a(n) for n = 1..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_04">Index entries for linear recurrences with constant coefficients</a>, signature (7,-18,20,-8).

%F a(n) = 7*a(n-1)-18*a(n-2)+20*a(n-3)-8*a(n-4). G.f.: -x*(4*x^3-10*x^2+5*x-1)/((x-1)*(2*x-1)^3). [_Colin Barker_, Oct 17 2012]

%t Table[(n-2) (n-3) 2^(n-2) + 2^n - 2, {n, 30}] (* _Vincenzo Librandi_, Mar 11 2013 *)

%o (Maxima) makelist((n-2)*(n-3)*2^(n-2)+2^n-2, n, 1, 30); /* _Martin Ettl_, Oct 15 2012 */

%o (MAGMA) [(n-2)*(n-3)*2^(n-2)+2^n-2: n in [1..30]]; // _Vincenzo Librandi_, Mar 11 2013

%K nonn,easy

%O 1,2

%A _N. J. A. Sloane_, Oct 13 2012

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Last modified April 23 03:26 EDT 2019. Contains 322380 sequences. (Running on oeis4.)