A374685 - OEIS

A374685

Numbers k such that the leaders of strictly increasing runs in the k-th composition in standard order are identical.

0, 1, 2, 3, 4, 6, 7, 8, 10, 12, 13, 14, 15, 16, 20, 24, 25, 27, 28, 29, 30, 31, 32, 36, 40, 42, 48, 49, 51, 52, 54, 55, 56, 57, 59, 60, 61, 62, 63, 64, 72, 80, 82, 84, 96, 97, 99, 102, 103, 104, 105, 108, 109, 110, 111, 112, 113, 115, 116, 118, 119, 120, 121

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OFFSET

1,3

COMMENTS

The leaders of strictly increasing runs in a sequence are obtained by splitting it into maximal strictly increasing subsequences and taking the first term of each.

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.

LINKS

Table of n, a(n) for n=1..63.

Gus Wiseman, Sequences counting and ranking compositions by their leaders (for six types of runs).

EXAMPLE

The maximal strictly increasing subsequences of the 6560th composition in standard order are ((1,3),(1,2,6)), with leaders (1,1), so 6560 is in the sequence.

The terms together with corresponding compositions begin:

0: ()

1: (1)

2: (2)

3: (1,1)

4: (3)

6: (1,2)

7: (1,1,1)

8: (4)

10: (2,2)

12: (1,3)

13: (1,2,1)

14: (1,1,2)

15: (1,1,1,1)

16: (5)

20: (2,3)

24: (1,4)

25: (1,3,1)

27: (1,2,1,1)

28: (1,1,3)

29: (1,1,2,1)

30: (1,1,1,2)

31: (1,1,1,1,1)

MATHEMATICA

stc[n_]:=Differences[Prepend[Join @@ Position[Reverse[IntegerDigits[n, 2]], 1], 0]]//Reverse;

Select[Range[0, 100], SameQ@@First/@Split[stc[#], Less]&]

CROSSREFS

The weak version is A374633, counted by A374631.

Positions of constant rows in A374683.

Compositions of this type are counted by A374686.

For distinct leaders we have A374698, counted by A374687.

The opposite version is A374759, counted by A374760.

Other types of runs: A272919 (counts A000005), A374519 (counts A374517), A374744 (counts A374742).

A011782 counts compositions.

A238130, A238279, A333755 count compositions by number of runs.

A374748 counts compositions by sum of leaders of weakly decreasing runs.

All of the following pertain to compositions in standard order:

- Length is A000120.

- Sum is A029837(n+1) (or sometimes A070939).

- Parts are listed by A066099.

- Adjacent equal pairs are counted by A124762, unequal A333382.

- Number of max runs: A124765, A124766, A124767, A124768, A124769, A333381.

- Ranks of anti-run compositions are A333489, counted by A003242.

- Run-length transform is A333627.

- Run-compression transform is A373948, sum A373953, excess A373954.

- Ranks of contiguous compositions are A374249, counted by A274174.

Cf. A065120, A106356, A238343, A333213, A373949, A374520, A374629, A374630, A374701, A374740, A374768.

Sequence in context: A275157 A374633 A368747 * A336824 A114149 A294652

Adjacent sequences: A374682 A374683 A374684 * A374686 A374687 A374688

KEYWORD

nonn

AUTHOR

Gus Wiseman, Jul 27 2024

STATUS

approved