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A137429
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a(n) = -2*a(n-1) - 2*a(n-2), with a(0)=1 and a(1)=-4.
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3
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1, -4, 6, -4, -4, 16, -24, 16, 16, -64, 96, -64, -64, 256, -384, 256, 256, -1024, 1536, -1024, -1024, 4096, -6144, 4096, 4096, -16384, 24576, -16384, -16384, 65536, -98304, 65536, 65536, -262144, 393216, -262144, -262144, 1048576, -1572864, 1048576, 1048576, -4194304, 6291456
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OFFSET
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0,2
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LINKS
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FORMULA
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For n >= 4, a(n) = -4*a(n-4).
G.f.: (1-2*x)/(1 + 2*x + 2*x^2).
a(n) = (1/2 + 3*i/2)*(-1 + i)^n + (1/2 - 3*i/2)*(-1 - i)^n, n >= 0, where i=sqrt(-1). - Taras Goy, Apr 20 2019
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MATHEMATICA
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LinearRecurrence[{-2, -2}, {1, -4}, 50] (* Harvey P. Dale, Mar 26 2013 *)
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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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