A356843 Numbers k such that the k-th composition in standard order covers an interval of positive integers (gapless) but contains no 1's.

2, 4, 8, 10, 16, 18, 20, 32, 36, 42, 64, 68, 72, 74, 82, 84, 128, 136, 146, 148, 164, 170, 256, 264, 272, 274, 276, 290, 292, 296, 298, 324, 328, 330, 338, 340, 512, 528, 548, 580, 584, 586, 594, 596, 658, 660, 676, 682, 1024, 1040, 1056, 1092, 1096, 1098

Offset

1,1

Comments

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..54.

Gus Wiseman, Statistics, classes, and transformations of standard compositions

Formula

Complement of A333217 in A356841.

Example

The terms together with their corresponding standard compositions begin:
    2: (2)
    4: (3)
    8: (4)
   10: (2,2)
   16: (5)
   18: (3,2)
   20: (2,3)
   32: (6)
   36: (3,3)
   42: (2,2,2)
   64: (7)
   68: (4,3)
   72: (3,4)
   74: (3,2,2)
   82: (2,3,2)
   84: (2,2,3)

Mathematica

nogapQ[m_]:=Or[m=={}, Union[m]==Range[Min[m], Max[m]]];
stc[n_]:=Differences[Prepend[Join@@Position[Reverse[IntegerDigits[n, 2]], 1], 0]]//Reverse;
Select[Range[100], !MemberQ[stc[#], 1]&&nogapQ[stc[#]]&]

Crossrefs

See link for sequences related to standard compositions.

A subset of A022340.

These compositions are counted by A251729.

The unordered version (using Heinz numbers of partitions) is A356845.

A333217 ranks complete compositions.

A356230 ranks gapless factorization lengths, firsts A356603.

A356233 counts factorizations into gapless numbers.

A356841 ranks gapless compositions, counted by A107428.

A356842 ranks non-gapless compositions, counted by A356846.

A356844 ranks compositions with at least one 1.

Cf. A053251, A055932, A073491, A073492, A073493, A137921, A356224/A356225.

Sequence in context: A125021 A085406 A022340 * A369492 A339608 A268497

Adjacent sequences: A356840 A356841 A356842 * A356844 A356845 A356846

Keyword

nonn

Author

Gus Wiseman, Sep 01 2022

Status

approved