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A164459
Number of binary strings of length n with no substrings equal to 0001 0011 or 1100.
1
13, 21, 35, 58, 96, 159, 264, 439, 730, 1215, 2023, 3369, 5612, 9349, 15576, 25952, 43241, 72050, 120054, 200043, 333329, 555423, 925499, 1542157, 2569695, 4281884, 7134907, 11888905, 19810501, 33010271, 55005074, 91655056, 152724992
OFFSET
4,1
FORMULA
G.f.: -x^4*(13-5*x-7*x^2-12*x^3+6*x^4-4*x^5+8*x^6) / ( (x^5+x^4+2*x^3+x^2-1)*(x-1)^2 ). - R. J. Mathar, Jan 19 2011
a(n) = 2*a(n-1)-2*a(n-4)+a(n-5)-a(n-6)+a(n-7). [Harvey P. Dale, May 06 2011]
MATHEMATICA
LinearRecurrence[{2, 0, 0, -2, 1, -1, 1}, {13, 21, 35, 58, 96, 159, 264}, 40] (*Harvey P. Dale, May 06 2011 *)
CROSSREFS
Sequence in context: A034292 A163113 A164496 * A164453 A164465 A164471
KEYWORD
nonn,easy
AUTHOR
R. H. Hardin, Aug 14 2009
STATUS
approved