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A178945
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Expansion of x*(1-x)^2/( (1-2*x^2)*(1-2*x)^2).
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1
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1, 2, 7, 16, 42, 96, 228, 512, 1160, 2560, 5648, 12288, 26656, 57344, 122944, 262144, 557184, 1179648, 2490624, 5242880, 11010560, 23068672, 48235520, 100663296, 209717248, 436207616, 905973760, 1879048192, 3892322304, 8053063680, 16643014656
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OFFSET
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1,2
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COMMENTS
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Let S(x) be the generating function for A000079. Then the generating function for this sequence is x(S(x)^2+S(x^2))/2.
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LINKS
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FORMULA
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a(n) = 2^(n-2)*n + 2^(n/2-5/2)*(1-(-1)^n).
a(n) = +4*a(n-1) -2*a(n-2) -8*a(n-3) +8*a(n-4).
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EXAMPLE
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(1, 4, 12, 32, 80, 192, 448, 1024,...) +
..(1, 0,..2,..0,..4,...0,...8,....0...) =
..(2, 4, 14, 32, 84, 192, 456, 1024,...). Then dividing the sum by 2 we obtain:
..(1, 2, 7, 16, 42, 96, 228,...).
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MATHEMATICA
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CoefficientList[Series[x (1-x)^2/((1-2x^2)(1-2x)^2), {x, 0, 50}], x] (* or *) LinearRecurrence[{4, -2, -8, 8}, {0, 1, 2, 7}, 50] (* Harvey P. Dale, Dec 29 2023 *)
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CROSSREFS
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KEYWORD
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nonn,easy
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AUTHOR
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STATUS
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approved
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