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A243482
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Number of isoscent sequences of length n with exactly nine descents.
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2
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1, 1842, 381540, 33260687, 1764436385, 67244544426, 2018462900473, 50530007996596, 1096301608172492, 21183116277395043, 371926458625987333, 6025302522233251390, 91147815762874899354, 1299862836761209689164, 17611186926254063273931, 228129250314546958924423
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OFFSET
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15,2
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LINKS
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MATHEMATICA
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b[n_, i_, t_] := b[n, i, t] = If[n < 1, 1, Expand[Sum[ If[j < i, x, 1] *b[n - 1, j, t + If[j == i, 1, 0]], {j, 0, t + 1}]]]; a[n_] := Coefficient[b[n - 1, 0, 0], x, 9]; Table[a[n], {n, 15, 40}] (* Jean-François Alcover, Feb 09 2015, after A242352 *)
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CROSSREFS
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KEYWORD
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nonn
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AUTHOR
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STATUS
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approved
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