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A124217
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Expansion of (1-x-x^2)/(1-2x-x^2+x^4).
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2
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1, 1, 2, 5, 11, 26, 61, 143, 336, 789, 1853, 4352, 10221, 24005, 56378, 132409, 310975, 730354, 1715305, 4028555, 9461440, 22221081, 52188297, 122569120, 287865097, 676078233, 1587833266, 3729175645, 8758319459, 20569736330
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OFFSET
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0,3
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COMMENTS
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Diagonal sums of generalized Pascal triangle A124216.
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LINKS
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FORMULA
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a(n)=sum{k=0..floor(n/2), sum{j=0..n-k, C(n-k,j)C(j,2(j-k))2^(j-k)}};
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MATHEMATICA
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CoefficientList[Series[(1-x-x^2)/(1-2x-x^2+x^4), {x, 0, 40}], x] (* or *) LinearRecurrence[{2, 1, 0, -1}, {1, 1, 2, 5}, 40] (* Harvey P. Dale, Jun 14 2016 *)
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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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