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A161718
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Expansion of (1+3*x^2)/(1+x)^2.
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2
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1, -2, 6, -10, 14, -18, 22, -26, 30, -34, 38, -42, 46, -50, 54, -58, 62, -66, 70, -74, 78, -82, 86, -90, 94, -98, 102, -106, 110, -114, 118, -122, 126, -130, 134, -138, 142, -146, 150, -154, 158, -162, 166, -170, 174, -178, 182, -186, 190, -194, 198, -202, 206, -210, 214, -218, 222, -226, 230, -234
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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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a(n) = -2*a(n-1)-a(n-2), n>3.
G.f.: (1+3*x^2)/(1+x)^2.
a(n) = 4*(-1)^n*n+2*(-1)^(n+1) = (-1)^n*A016825(n-1), n>0. (End)
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MATHEMATICA
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CoefficientList[Series[(1+3*x^2)/(1+x)^2, {x, 0, 80}], x] (* or *) LinearRecurrence[ {-2, -1}, {1, -2, 6}, 80] (* Harvey P. Dale, Mar 19 2016 *)
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PROG
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(PARI) x='x+O('x^99); Vec((1+3*x^2)/(1+x)^2) \\ Altug Alkan, Apr 17 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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Pr Mosbah Amlouk (Mosbah.Amlouk(AT)fsb.rnu.tn), Jun 17 2009
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EXTENSIONS
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STATUS
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approved
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