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A348405
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a(0) = 1, a(n) + a(n+1) = round(2^n/9), n >= 0.
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2
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1, -1, 1, -1, 2, 0, 4, 3, 11, 17, 40, 74, 154, 301, 609, 1211, 2430, 4852, 9712, 19415, 38839, 77669, 155348, 310686, 621382, 1242753, 2485517, 4971023, 9942058, 19884104, 39768220, 79536427, 159072867, 318145721, 636291456, 1272582898, 2545165810
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OFFSET
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0,5
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LINKS
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FORMULA
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G.f.: (x^4-x^3+2x-1)/((2*x^3-3*x^2+3*x-1)*(x+1)^2).
A172481(n) = Sum_{k=0..n} (-1)^(n-k)*binomial(n, k)*a(2*n-k). With negative sign for ...*a(1+2*n-k) and ...*a(3+2*n-k) too.
A175656(n) = Sum_{k=0..n} (-1)^(n-k)*binomial(n, k)*a(2+2*n-k).
A136298(n+1) = Sum_{k=0..n} (-1)^(n-k)*binomial(n, k)*a(4+2*n-k).
A348407(n) = Sum_{k=0..n} (-1)^(n-k)*binomial(n, k)*(a(2+2*n-k) - 2*a(1+2*n-k) - a(2*n-k)).
(End)
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MATHEMATICA
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CoefficientList[ Series[(x^4-x^3+2x-1)/((2*x^3-3*x^2+3*x-1)*(x+1)^2), {x, 0, 40}], x] (* Thomas Scheuerle, Oct 17 2021 *)
nxt[{n_, a_}]:={n+1, Round[(2^n)/9]-a}; NestList[nxt, {0, 1}, 40][[All, 2]] (* or *) LinearRecurrence[{1, 2, -1, 1, 2}, {1, -1, 1, -1, 2}, 40] (* Harvey P. Dale, Apr 28 2022 *)
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CROSSREFS
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Cf. A139797 (a(n) + a(n+1) = round(2^n/9) too, but a(0) = 0).
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KEYWORD
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sign
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AUTHOR
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EXTENSIONS
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STATUS
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approved
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