OFFSET
1,3
COMMENTS
The leaders of strictly decreasing runs in a sequence are obtained by splitting it into maximal strictly decreasing 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
EXAMPLE
The 10000000th composition in standard order is (3,1,4,3,2,1,2,8), with strictly decreasing runs ((3,1),(4,3,2,1),(2),(8)), with leaders (3,4,2,1) so 10000000 is in the sequence.
The terms together with the corresponding compositions begin:
0: ()
1: (1)
2: (2)
4: (3)
5: (2,1)
6: (1,2)
8: (4)
9: (3,1)
11: (2,1,1)
12: (1,3)
13: (1,2,1)
16: (5)
17: (4,1)
18: (3,2)
19: (3,1,1)
20: (2,3)
24: (1,4)
25: (1,3,1)
MATHEMATICA
stc[n_]:=Differences[Prepend[Join @@ Position[Reverse[IntegerDigits[n, 2]], 1], 0]]//Reverse;
Select[Range[0, 100], UnsameQ@@First/@Split[stc[#], Greater]&]
CROSSREFS
Compositions of this type are counted by A374761.
All of the following pertain to compositions in standard order:
- Length is A000120.
- Sum is A029837(n+1).
- Parts are listed by A066099.
Six types of runs:
KEYWORD
nonn
AUTHOR
Gus Wiseman, Jul 29 2024
STATUS
approved