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A321116
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Number of permutations p of [n] such that in 0p the largest up-jump equals nine xx and no down-jump is larger than 2.
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2
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672, 5454, 40272, 283688, 1948408, 13188482, 88469166, 589852620, 3914957358, 25886899652, 170722453774, 1123938295984, 7390061858416, 48546948619410, 318711158282218, 2091405520367970, 13719823343200698, 89986405527666712, 590148303249975384
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OFFSET
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9,1
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LINKS
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MAPLE
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b:= proc(u, o, k) option remember; `if`(u+o=0, 1,
add(b(u-j, o+j-1, k), j=1..min(2, u))+
add(b(u+j-1, o-j, k), j=1..min(k, o)))
end:
a:= n-> (k-> b(0, n, k)-b(0, n, k-1))(9):
seq(a(n), n=9..30);
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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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