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A352514
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Number of strong nonexcedances (parts below the diagonal) of the n-th composition in standard order.
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16
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0, 0, 0, 1, 0, 1, 0, 2, 0, 1, 0, 2, 0, 1, 2, 3, 0, 1, 0, 2, 0, 1, 2, 3, 0, 1, 1, 2, 1, 3, 3, 4, 0, 1, 0, 2, 0, 1, 2, 3, 0, 1, 1, 2, 1, 3, 3, 4, 0, 1, 1, 2, 0, 2, 2, 3, 1, 2, 3, 4, 3, 4, 4, 5, 0, 1, 0, 2, 0, 1, 2, 3, 0, 1, 1, 2, 1, 3, 3, 4, 0, 1, 1, 2, 0, 2, 2
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OFFSET
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0,8
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COMMENTS
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The k-th composition in standard order (graded reverse-lexicographic, A066099) is obtained by taking the set of positions of 1's in the reversed binary expansion of k, prepending 0, taking first differences, and reversing again. This gives a bijective correspondence between nonnegative integers and integer compositions. See also A000120, A059893, A070939, A114994, A225620.
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LINKS
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EXAMPLE
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The 83rd composition in standard order is (2,3,1,1), with strong nonexcedances {3,4}, so a(83) = 2.
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MATHEMATICA
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stc[n_]:=Differences[Prepend[Join@@ Position[Reverse[IntegerDigits[n, 2]], 1], 0]]//Reverse;
pa[y_]:=Length[Select[Range[Length[y]], #>y[[#]]&]];
Table[pa[stc[n]], {n, 0, 30}]
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CROSSREFS
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Positions of first appearances are A000225.
The triangle A352521 counts these compositions (first column A219282).
A008292 is the triangle of Eulerian numbers (version without zeros).
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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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