A217527 a(n) = 2^(n-2)*(n-2)^2+2^(n-1).

2, 6, 24, 88, 288, 864, 2432, 6528, 16896, 42496, 104448, 251904, 598016, 1400832, 3244032, 7438336, 16908288, 38141952, 85458944, 190316544, 421527552, 929038336, 2038431744, 4454350848, 9697230848, 21038628864, 45499809792, 98113159168, 210990268416

Offset

2,1

Links

Vincenzo Librandi, Table of n, a(n) for n = 2..1000

W. Griffiths, R. Smith and D. Warren, Almost avoiding pairs of permutations, PU. M. A. Vol. 22 (2011), 129-139.

Index entries for linear recurrences with constant coefficients, signature (6,-12,8).

Formula

a(n) = 6*a(n-1)-12*a(n-2)+8*a(n-3). G.f.: -2*x^2*(6*x^2-3*x+1)/(2*x-1)^3. [Colin Barker, Oct 17 2012]

Mathematica

Table[2^(n-2) (n-2)^2 + 2^(n-1), {n, 2, 30}] (* Vincenzo Librandi, Mar 11 2013 *)

Prog

(Maxima) makelist(2^(n-2)*(n-2)^2+2^(n-1), n, 2, 30); /* Martin Ettl, Oct 15 2012 */
(Magma) [2^(n-2)*(n-2)^2+2^(n-1): n in [2..30]]; // Vincenzo Librandi, Mar 11 2013

Crossrefs

Sequence in context: A048120 A322198 A003759 * A293774 A226037 A003450

Adjacent sequences: A217524 A217525 A217526 * A217528 A217529 A217530

Keyword

nonn,easy

Author

N. J. A. Sloane, Oct 13 2012

Status

approved