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A098507
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Diagonal sums of the number triangle A098505.
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1
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1, 1, 2, 2, 5, 6, 10, 9, 19, 22, 65, 88, 114, 187, 395, 376, 888, 520, 2645, 2017, 3303, 3590, 8820, 9408, 5785, 7792, 24181, 27047, 74720, 68731, 153394, 159394, 369957, 1261522, 4326030, 4924898, 6538595, 9754155, 10068484, 10541264, 24936678
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OFFSET
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0,3
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LINKS
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FORMULA
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a(n) = Sum_{k=0..floor(n/2)} numerator((n-k+1)*binomial(n-k, k)/binomial(2*n-2*k, n-k)).
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MATHEMATICA
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Table[Sum[Numerator[(n-k+1) Binomial[n-k, k]/Binomial[2n-2k, n-k]], {k, 0, Floor[ n/2]}], {n, 0, 60}] (* Harvey P. Dale, Jun 19 2021 *)
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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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