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 A164464 Number of binary strings of length n with no substrings equal to 0001, 0100, or 0111. 1
 13, 20, 31, 47, 70, 104, 154, 227, 334, 491, 721, 1058, 1552, 2276, 3337, 4892, 7171, 10511, 15406, 22580, 33094, 48503, 71086, 104183, 152689, 223778, 327964, 480656, 704437, 1032404, 1513063, 2217503, 3249910, 4762976, 6980482, 10230395 (list; graph; refs; listen; history; text; internal format)
 OFFSET 4,1 LINKS R. H. Hardin, Table of n, a(n) for n = 4..500 Index entries for linear recurrences with constant coefficients, signature (2,-1,1,-1). FORMULA G.f.: x^4*(13 - 6*x + 4*x^2 - 8*x^3)/( (1-x)*(1-x-x^3) ). - R. J. Mathar, Jan 19 2011 a(n) = a(n-1) + a(n-3) + 3 for n>6. - Greg Dresden, Feb 09 2020 a(n) = b(n+2) + b(n+1) + 2*b(n) - 3, where b(n) = A000930(n). - G. C. Greubel, Feb 09 2020 MAPLE m:=40; S:=series(x^4*(13-6*x+4*x^2-8*x^3)/((1-x)*(1-x-x^3)), x, m+1): seq(coeff(S, x, j), j=4..m); # G. C. Greubel, Feb 09 2020 MATHEMATICA LinearRecurrence[{2, -1, 1, -1}, {13, 20, 31, 47}, 40] (* G. C. Greubel, Feb 09 2020 *) PROG (PARI) Vec( x^4*(13-6*x+4*x^2-8*x^3)/((1-x)*(1-x-x^3)) +O('x^40) ) \\ G. C. Greubel, Feb 09 2020 (MAGMA) R:=PowerSeriesRing(Integers(), 40); Coefficients(R!( x^4*(13-6*x+4*x^2-8*x^3)/((1-x)*(1-x-x^3)) )); // G. C. Greubel, Feb 09 2020 (Sage) def A164464_list(prec):     P. = PowerSeriesRing(ZZ, prec)     return P( x^4*(13-6*x+4*x^2-8*x^3)/((1-x)*(1-x-x^3)) ).list() a=A164464_list(40); a[4:] # G. C. Greubel, Feb 09 2020 (GAP) a:=[13, 20, 31, 47];; for n in [5..40] do a[n]:=2*a[n-1]-a[n-2]+a[n-3] -a[n-4]; od; a; # G. C. Greubel, Feb 09 2020 CROSSREFS Cf. A000930. Sequence in context: A164483 A164468 A164489 * A164467 A164505 A164484 Adjacent sequences:  A164461 A164462 A164463 * A164465 A164466 A164467 KEYWORD nonn AUTHOR R. H. Hardin, Aug 14 2009 STATUS approved

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Last modified June 24 21:50 EDT 2021. Contains 345433 sequences. (Running on oeis4.)