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A115451
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Expansion of 1/((1+x)*(1-2*x)*(1+x^2)).
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9
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1, 1, 2, 4, 9, 17, 34, 68, 137, 273, 546, 1092, 2185, 4369, 8738, 17476, 34953, 69905, 139810, 279620, 559241, 1118481, 2236962, 4473924, 8947849, 17895697, 35791394, 71582788, 143165577, 286331153, 572662306, 1145324612, 2290649225, 4581298449, 9162596898
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OFFSET
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0,3
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COMMENTS
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LINKS
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FORMULA
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a(n) = a(n-1) + a(n-2) + a(n-3) + 2*a(n-4);
a(n) = Sum_{k=0..n} (2^(n-k+1)-1)(-1)^k} - Sum_{k=0..floor(n/2)} (2^(n-2k)-1)(-1)^k}.
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MATHEMATICA
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LinearRecurrence[{1, 1, 1, 2}, {1, 1, 2, 4}, 50] (* Harvey P. Dale, Oct 22 2011 *)
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PROG
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(PARI) x='x+O('x^50); Vec(1/((1+x)*(1-2*x)*(1+x^2))) \\ G. C. Greubel, Sep 26 2017
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CROSSREFS
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KEYWORD
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easy,nonn
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AUTHOR
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STATUS
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approved
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