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 A233247 Expansion of ( 1-x^3-x^2 ) / ( (x^3-x^2-1)*(x^3+2*x^2+x-1) ). 2
 1, 1, 1, 4, 9, 16, 36, 81, 169, 361, 784, 1681, 3600, 7744, 16641, 35721, 76729, 164836, 354025, 760384, 1633284, 3508129, 7535025, 16184529, 34762816, 74666881, 160376896, 344473600, 739894401, 1589218225, 3413480625, 7331811876, 15747991081, 33825095056 (list; graph; refs; listen; history; text; internal format)
 OFFSET 0,4 COMMENTS a(n) is the number of tilings of a 3 X 2 X n room with bricks of 1 X 1 X 3 shape (and in that respect a generalization of A028447 which fills 3 X 2 X n rooms with bricks of 1 X 1 X 2 shape). The inverse INVERT transform is 1, 0, 3, 2, 2, 4, 4, 6, 8, 10, .. , continued as in A068924. LINKS G. C. Greubel, Table of n, a(n) for n = 0..1000 R. J. Mathar, Tilings of rectangular regions by rectangular tiles: counts derived from transfer matrices, arXiv:1406.7788 [math.CO], 2014, see eq. (39). Index entries for linear recurrences with constant coefficients, signature (1,1,3,1,-1,-1). FORMULA a(n) = A000930(n)^2. MAPLE A233247 := proc(n)     A000930(n)^2 ; end proc: # second Maple program: a:= n-> (<<0|1|0>, <0|0|1>, <1|0|1>>^n)[3, 3]^2: seq(a(n), n=0..40);  # Alois P. Heinz, Dec 06 2013 MATHEMATICA Table[Sum[Binomial[n-2i, i], {i, 0, n/3}]^2, {n, 0, 50}] (* Wesley Ivan Hurt, Dec 06 2013 *) LinearRecurrence[{1, 1, 3, 1, -1, -1}, {1, 1, 1, 4, 9, 16}, 40] (* Harvey P. Dale, Jan 14 2015 *) CoefficientList[Series[(1-x^3-x^2)/((x^3-x^2-1)*(x^3+2*x^2+x-1)), {x, 0, 50}], x] (* G. C. Greubel, Apr 29 2017 *) PROG (PARI) x='x+O('x^50); Vec((1-x^3-x^2)/((x^3-x^2-1)*(x^3+2*x^2+x-1))) \\ G. C. Greubel, Apr 29 2017 CROSSREFS Cf. A000930. Sequence in context: A204503 A138858 A076967 * A231180 A250029 A111378 Adjacent sequences:  A233244 A233245 A233246 * A233248 A233249 A233250 KEYWORD easy,nonn AUTHOR R. J. Mathar, Dec 06 2013 STATUS approved

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Last modified January 24 11:16 EST 2021. Contains 340399 sequences. (Running on oeis4.)