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A217527 a(n) = 2^(n-2)*(n-2)^2+2^(n-1). 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 (list; graph; refs; listen; history; text; internal format)
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

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Last modified April 23 18:34 EDT 2019. Contains 322387 sequences. (Running on oeis4.)