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A330033
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a(n) = Kronecker(n, 5) * (-1)^floor(n/5).
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0
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0, 1, -1, -1, 1, 0, -1, 1, 1, -1, 0, 1, -1, -1, 1, 0, -1, 1, 1, -1, 0, 1, -1, -1, 1, 0, -1, 1, 1, -1, 0, 1, -1, -1, 1, 0, -1, 1, 1, -1, 0, 1, -1, -1, 1, 0, -1, 1, 1, -1, 0, 1, -1, -1, 1, 0, -1, 1, 1, -1, 0, 1, -1, -1, 1, 0, -1, 1, 1, -1, 0, 1, -1, -1, 1, 0, -1
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OFFSET
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0,1
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COMMENTS
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This is a strong elliptic divisibility sequence t_n as given in [Kimberling, p. 16] where x = y = z = -1.
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LINKS
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FORMULA
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Euler transform of length 10 sequence [-1, -1, 0, 0, -1, 0, 0, 0, 0, 1].
G.f.: (x - 2*x^2 + x^3) / (1 - x + x^2 - x^3 + x^4) = x * (1 - x) * (1 - x^2) / (1 + x^5).
0 = a(n)*a(n-4) - a(n-1)*a(n-3) - a(n-2)*a(n-2) for all n in Z.
0 = a(n)*a(n+5) + a(n+1)*a(n+4) - a(n+2)*a(n+3) for all n in Z.
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EXAMPLE
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G.f. = x - x^2 - x^3 + x^4 - x^6 + x^7 + x^8 - x^9 + x^11 - x^12 + ...
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MATHEMATICA
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a[ n_] := {1, -1, -1, 1, 0}[[Mod[n, 5, 1]]] (-1)^Quotient[n, 5];
a[ n_] := JacobiSymbol[n, 5] (-1)^Quotient[n, 5];
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PROG
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(PARI) {a(n) = [0, 1, -1, -1, 1][n%5 + 1] * (-1)^(n\5)};
(PARI) {a(n) = kronecker(n, 5) * (-1)^(n\5)};
(Magma) [KroneckerSymbol(n, 5) * (-1)^Floor(n/5):n in [0..76]]; // Marius A. Burtea, Nov 28 2019
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CROSSREFS
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KEYWORD
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sign,easy
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AUTHOR
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STATUS
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approved
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