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 A097926 Number of (n,4) Freiman-Wyner sequences. 3

%I

%S 18,36,70,134,258,498,960,1850,3566,6874,13250,25540,49230,94894,

%T 182914,352578,679616,1310002,2525110,4867306,9382034,18084452,

%U 34858902,67192694,129518082,249654130,481223808,927588714,1787984734,3446451386

%N Number of (n,4) Freiman-Wyner sequences.

%C "The values for n <= 4 are straightforward."

%D I. F. Blake, The enumeration of certain run length sequences, Information and Control, 55 (1982), 222-237.

%F a(n) = 2a(n-1) - a(n-k-1), k=4, n >= 2k+2. - _R. J. Mathar_, Oct 31 2006

%F G.f.: -2*(5*x^3+8*x^2+9*x+9)*x^5/(x^4+x^3+x^2+x-1) = -10*x^4-6*x^3-2*x^2-2+(-2*x^3-2+2*x)/(x^4+x^3+x^2+x-1). - _R. J. Mathar_, Nov 18 2007

%p A097926 := proc(nmax) local a,n,k; k := 4 ; a := [18,36,70,134,258] ; while nops(a) < nmax do n := nops(a)+k+1 ; a := [op(a),2*op(n-1-k,a)-op(n-2*k-1,a) ] ; od ; end: nmax := 30 ; a := A097926(nmax) ; for i from 1 to nmax do printf("%d,",op(i,a)) ; od: # _R. J. Mathar_, Oct 31 2006

%Y Cf. A006355, A097925.

%K nonn

%O 5,1

%A _N. J. A. Sloane_, Sep 05 2004

%E Corrected and extended by _R. J. Mathar_, Oct 31 2006

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Last modified September 27 12:30 EDT 2020. Contains 337380 sequences. (Running on oeis4.)