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Number of binary words of length n which have no 0^b 1 1 0^a 1 0 1 0^b - matches, where a=b=2.
2

%I #21 Sep 08 2022 08:46:06

%S 1,2,4,8,16,32,64,128,256,512,1024,2047,4092,8180,16352,32688,65344,

%T 130624,261120,521984,1043457,2085893,4169745,8335410,16662664,

%U 33309024,66585456,133105760,266081280,531902207,1063283962,2125527529,4248975286,8493793063

%N Number of binary words of length n which have no 0^b 1 1 0^a 1 0 1 0^b - matches, where a=b=2.

%H Alois P. Heinz, <a href="/A234592/b234592.txt">Table of n, a(n) for n = 0..1000</a>

%H B. K. Miceli, J, Remmel, <a href="http://puma.dimai.unifi.it/23_3/miceli_remmel.pdf">Minimal Overlapping Embeddings and Exact Matches in Words</a>, PU. M. A., Vol. 23 (2012), No. 3, pp. 291-315.

%H <a href="/index/Rec#order_11">Index entries for linear recurrences with constant coefficients</a>, signature (2,0,0,0,0,0,0,0,-1,1,1).

%F G.f.: (1+x^9+x^10)/(1-2*x+x^9-x^10-x^11). - _Alois P. Heinz_, Jan 08 2014

%p a:= n-> coeff(series(-(x^10+x^9+1)/(x^11+x^10-x^9+2*x-1), x, n+1), x, n):

%p seq(a(n), n=0..40); # _Alois P. Heinz_, Jan 08 2014

%t a[n_ /; n<=10]:= 2^n; a[n_]:=a[n] =2*a[n-1] -a[n-9] +a[n-10] +a[n-11]; Table[a[n], {n, 0, 40}] (* _Jean-François Alcover_, Mar 18 2014 *)

%t LinearRecurrence[{2,0,0,0,0,0,0,0,-1,1,1}, {1,2,4,8,16,32,64,128,256, 512,1024}, 40] (* _Harvey P. Dale_, May 17 2018 *)

%o (PARI) my(x='x+O('x^40)); Vec((1+x^9+x^10)/(1-2*x+x^9-x^10-x^11)) \\ _G. C. Greubel_, Sep 14 2019

%o (Magma) R<x>:=PowerSeriesRing(Integers(), 40); Coefficients(R!( (1+x^9+x^10)/(1-2*x+x^9-x^10-x^11) )); // _G. C. Greubel_, Sep 14 2019

%o (Sage)

%o def A234592_list(prec):

%o P.<x> = PowerSeriesRing(ZZ, prec)

%o return P((1+x^9+x^10)/(1-2*x+x^9-x^10-x^11)).list()

%o A234592_list(40) # _G. C. Greubel_, Sep 14 2019

%o (GAP) a:=[1,2,4,8,16,32,64,128,256,512,1024];; for n in [12..40] do a[n]:=2*a[n-1]-a[n-9]+a[n-10]+a[n-11]; od; a; # _G. C. Greubel_, Sep 14 2019

%K nonn,easy

%O 0,2

%A _N. J. A. Sloane_, Jan 01 2014

%E a(17)-a(33) from _Alois P. Heinz_, Jan 08 2014