OFFSET
4,1
LINKS
Vincenzo Librandi, Table of n, a(n) for n = 4..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
From Colin Barker, Oct 17 2012: (Start)
a(n) = 6*a(n-1) - 12*a(n-2) + 8*a(n-3).
G.f.: -x^4*(44*x^2 - 52*x + 23)/(2*x-1)^3. (End)
MATHEMATICA
Table[2^(n-4) (4 n^2 - 16 n + 23), {n, 4, 30}] (* Vincenzo Librandi, Mar 11 2013 *)
LinearRecurrence[{6, -12, 8}, {23, 86, 284}, 30] (* Harvey P. Dale, Oct 06 2019 *)
PROG
(Maxima) makelist(2^(n-4)*(4*n^2-16*n+23), n, 4, 30); /* Martin Ettl, Oct 15 2012 */
(Magma) [2^(n-4)*(4*n^2-16*n+23): n in [4..30]]; // Vincenzo Librandi, Mar 11 2013
CROSSREFS
KEYWORD
nonn,easy
AUTHOR
N. J. A. Sloane, Oct 13 2012
STATUS
approved