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 A080204 Number of fixed points under n-fold inflation for the substitution rule a->abc, b->ab, c->b that underlies the Kolakoski (3,1) sequence. 2
 1, 3, 10, 23, 51, 114, 253, 559, 1234, 2723, 6007, 13250, 29225, 64459, 142170, 313567, 691595, 1525362, 3364293, 7420183, 16365730, 36095755, 79611695, 175589122, 387274001, 854159699, 1883908522, 4155091047, 9164341795, 20212592114, 44580275277, 98324892351, 216862376818 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,2 COMMENTS See Baake-Sing (2002/2003) for the Kolakowski sequence. a(n) is the number of possible tilings of a bracelet of "thickness" 1 and length n using single-color squares, single-color dominoes, and two-color k-ominoes with k >= 3. - Michael Tulskikh and Greg Dresden, Sep 03 2019; edited by Greg Dresden, Feb 18 2020, May 14 2020, May 18 2020 LINKS Metin Sariyar, Table of n, a(n) for n = 1..300 J. E. Anderson and I. F. Putnam, Topological invariants for substitution tilings and their associated C*-algebras, Ergod. Theory and Dyn. Systems 18 (1998) 509-537. See also, Technical report DMS-720-IR, University of Victoria, 1995. Michael Baake and B. Sing, Kolakoski-(3,1) is a (deformed) model set, arXiv:math/0206098 [math.MG], 2002-2003. Greg Dresden and Michael Tulskikh, Tilings of 2 X n boards with dominos and L-shaped trominos, Washington & Lee University (2021). Index entries for linear recurrences with constant coefficients, signature (3,-2,1,-1). FORMULA Obtained from dynamical zeta function Z(x)=(1-x)/(1-2x-x^3), so that x Z'(x)/Z(x) is the ordinary power series generating function. From Colin Barker, Jul 02 2012: (Start) a(n) = 3*a(n-1) - 2*a(n-2) + a(n-3) - a(n-4). G.f.: x*(1+3*x^2-2*x^3)/((1-x)*(1-2*x-x^3)). (End) a(n) = n*Sum_{m=1..n} Sum_{i=0..(n-m)/2} binomial(m,i)*binomial(n-2*i-1,m-1)/m. - Vladimir Kruchinin, Mar 10 2015 a(n) = 2*a(n-1) + a(n-3) + 2. - Greg Dresden, Feb 08 2020 a(n) = w1^n + w2^n + w3^n - 1, for w1, w2, w3 roots of x^3-2x^2-1=0. - Greg Dresden, Feb 18 2020 MATHEMATICA CoefficientList[Series[(1 + 3 x^2 - 2 x^3) / ((1 - x) (1 - 2 x - x^3)), {x, 0, 40}], x] (* Vincenzo Librandi, Mar 12 2015 *) PROG (PARI) x='x+O('x^66); Vec(x*(1+3*x^2-2*x^3)/((1-x)*(1-2*x-x^3))) \\ Joerg Arndt, Jun 15 2013 (Maxima) a(n):=(n*sum(sum(binomial(m, i)*binomial(n-2*i-1, m-1), i, 0, (n-m)/2)/m, m, 1, n)); /* Vladimir Kruchinin, Mar 10 2015 */ (Magma) I:=[1, 3, 10, 23]; [n le 4 select I[n] else 3*Self(n-1)-2*Self(n-2)+Self(n-3)-Self(n-4): n in [1..40]]; // Vincenzo Librandi, Mar 12 2015 CROSSREFS Equals one less than A332647. Sequence in context: A256525 A192973 A294503 * A115982 A167243 A316403 Adjacent sequences:  A080201 A080202 A080203 * A080205 A080206 A080207 KEYWORD easy,nonn AUTHOR Michael Baake and Uwe Grimm, Mar 20 2003 STATUS approved

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Last modified July 6 12:26 EDT 2022. Contains 355110 sequences. (Running on oeis4.)