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A322039
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Expansion of (1 + x)^2 / ((1 - x)^2*(1 + 2*x)^2).
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2
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1, 0, 4, -4, 16, -28, 72, -148, 336, -716, 1560, -3332, 7136, -15164, 32168, -67956, 143216, -300972, 631096, -1320420, 2757376, -5747740, 11961544, -24855124, 51574416, -106877068, 221210712, -457334468, 944495136, -1948642556
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OFFSET
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0,3
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COMMENTS
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Connected with tiling of torus by squares (see A322038).
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LINKS
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FORMULA
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a(n) = -2*a(n-1) + 3*a(n-2) + 4*a(n-3) - 4*a(n-4) for n>3.
a(n) = (16 + 11*(-2)^n + 3*(4+(-2)^n)*n) / 27.
(End)
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MATHEMATICA
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LinearRecurrence[{-2, 3, 4, -4}, {1, 0, 4, -4}, 100] (* Amiram Eldar, Dec 04 2018 *)
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PROG
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(PARI) Vec((1 + x)^2 / ((1 - x)^2*(1 + 2*x)^2) + O(x^40)) \\ Colin Barker, Dec 04 2018
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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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