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 A097926 Number of (n,4) Freiman-Wyner sequences. 3
 18, 36, 70, 134, 258, 498, 960, 1850, 3566, 6874, 13250, 25540, 49230, 94894, 182914, 352578, 679616, 1310002, 2525110, 4867306, 9382034, 18084452, 34858902, 67192694, 129518082, 249654130, 481223808, 927588714, 1787984734, 3446451386 (list; graph; refs; listen; history; text; internal format)
 OFFSET 5,1 COMMENTS "The values for n <= 4 are straightforward." REFERENCES I. F. Blake, The enumeration of certain run length sequences, Information and Control, 55 (1982), 222-237. LINKS FORMULA a(n) = 2a(n-1) - a(n-k-1), k=4, n >= 2k+2. - R. J. Mathar, Oct 31 2006 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 MAPLE 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 CROSSREFS Cf. A006355, A097925. Sequence in context: A008600 A131766 A154575 * A087967 A070224 A083211 Adjacent sequences:  A097923 A097924 A097925 * A097927 A097928 A097929 KEYWORD nonn AUTHOR N. J. A. Sloane, Sep 05 2004 EXTENSIONS Corrected and extended by R. J. Mathar, Oct 31 2006 STATUS approved

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Last modified June 1 00:27 EDT 2020. Contains 334756 sequences. (Running on oeis4.)