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A089932
G.f.: (1-x)^5/((-1+4*x-3*x^2+x^3)*(1-3*x+x^2)*(-1+2*x)).
3
1, 4, 16, 60, 215, 747, 2539, 8491, 28049, 91782, 298109, 962594, 3093687, 9905444, 31619072, 100681587, 319944693, 1015039586, 3215903436, 10177462312, 32179381609, 101668695088, 321014982282, 1013068488800, 3195703133266, 10077204123667, 31767718475161
OFFSET
0,2
LINKS
A. Burstein and T. Mansour, Words restricted by 3-letter generalized multipermutation patterns, Annals. Combin., 7 (2003), 1-14. See Th. 3.6, case k=4.
MATHEMATICA
CoefficientList[Series[(1-x)^5/((-1+4x-3x^2+x^3)(1-3x+x^2)(-1+2x)), {x, 0, 30}], x] (* or *) LinearRecurrence[{9, -30, 46, -34, 13, -2}, {1, 4, 16, 60, 215, 747}, 30] (* Harvey P. Dale, May 20 2015 *)
CROSSREFS
KEYWORD
nonn,easy
AUTHOR
N. J. A. Sloane, Jan 18 2004
STATUS
approved