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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
OFFSET
2,1
LINKS
W. Griffiths, R. Smith and D. Warren, Almost avoiding pairs of permutations, PU. M. A. Vol. 22 (2011), 129-139.
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
KEYWORD
nonn,easy
AUTHOR
N. J. A. Sloane, Oct 13 2012
STATUS
approved