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A354908
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Numbers k such that the k-th composition in standard order (graded reverse-lexicographic, A066099) is collapsible.
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2
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1, 2, 3, 4, 7, 8, 10, 11, 14, 15, 16, 31, 32, 36, 39, 42, 43, 46, 47, 58, 59, 60, 62, 63, 64, 127, 128, 136, 138, 139, 142, 143, 168, 170, 171, 174, 175, 184, 186, 187, 190, 191, 232, 234, 235, 238, 239, 248, 250, 251, 254, 255, 256, 292, 295, 316, 319, 484
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OFFSET
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1,2
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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.
If a collapse is an adding together of some partial run of an integer composition c, we say c is collapsible iff by some sequence of collapses it can be reduced to a single part. An example of such a sequence of collapses is (11132112) -> (332112) -> (33222) -> (6222) -> (66) -> (n), which shows that (11132112) is a collapsible composition of 12.
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LINKS
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EXAMPLE
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The terms together with their corresponding compositions begin:
1:(1) 2:(2) 4:(3) 8:(4) 16:(5) 32:(6)
3:(11) 7:(111) 10:(22) 31:(11111) 36:(33)
11:(211) 39:(3111)
14:(112) 42:(222)
15:(1111) 43:(2211)
46:(2112)
47:(21111)
58:(1122)
59:(11211)
60:(1113)
62:(11112)
63:(111111)
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MATHEMATICA
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repcams[q_List]:=repcams[q]=Union[{q}, If[UnsameQ@@q, {}, Union@@repcams/@Union[Insert[Drop[q, #], Plus@@Take[q, #], First[#]]&/@Select[Tuples[Range[Length[q]], 2], And[Less@@#, SameQ@@Take[q, #]]&]]]];
stc[n_]:=Differences[Prepend[Join@@ Position[Reverse[IntegerDigits[n, 2]], 1], 0]]//Reverse;
Select[Range[0, 100], MemberQ[repcams[stc[#]], {_}]&]
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CROSSREFS
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The version for Heinz numbers of partitions is A300273, counted by A275870.
These compositions are counted by A353860.
A124767 counts runs in standard compositions.
A334968 counts distinct sums of subsequences of standard compositions.
A351014 counts distinct runs of standard compositions, firsts A351015.
A354582 counts distinct partial runs of standard compositions, sums A354907.
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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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