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A168052
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Hankel transform of a Motzkin variant.
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2
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1, -1, 2, -3, 3, -4, 5, -5, 6, -7, 7, -8, 9, -9, 10, -11, 11, -12, 13, -13, 14, -15, 15, -16, 17, -17, 18, -19, 19, -20, 21, -21, 22, -23, 23, -24, 25, -25, 26, -27, 27, -28, 29, -29, 30, -31, 31, -32, 33, -33, 34, -35, 35, -36, 37, -37, 38, -39, 39, -40, 41, -41, 42, -43
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OFFSET
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0,3
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COMMENTS
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LINKS
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FORMULA
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G.f.: (1+x^2)/((1+x)^2*(1-x+x^2)).
a(n) = cos(Pi*n/3)/3 + sqrt(3)*sin(Pi*n/3)/9 + 2*(n+1)*(-1)^n/3.
E.g.f.: exp(-x)*(6 - 6*x + exp(3*x/2)*(3*cos(sqrt(3)*x/2) + sqrt(3)*sin(sqrt(3)*x/2)))/9. - Stefano Spezia, Apr 03 2023
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MATHEMATICA
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LinearRecurrence[{-1, 0, -1, -1}, {1, -1, 2, -3}, 100] (* G. C. Greubel, Jul 07 2016 *)
CoefficientList[Series[(1 + x^2) / ((1 + x)^2 (1 - x + x^2)), {x, 0, 80}], x] (* Vincenzo Librandi, Jul 08 2016 *)
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PROG
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(Magma) I:=[1, -1, 2, -3]; [n le 4 select I[n] else - Self(n-1)-Self(n-3)- Self(n-4): n in [1..65]]; // Vincenzo Librandi, Jul 08 2016
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CROSSREFS
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KEYWORD
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easy,sign
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AUTHOR
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STATUS
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approved
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