OFFSET
1,2
LINKS
EXAMPLE
The sets are the columns below:
1 2 1 3 1 2 1 4 1 2 3 1 1 2 1 5 1 2 3 4 1 1 1 2 2 3 1
2 3 3 2 4 4 4 2 3 3 2 5 5 5 5 2 3 4 3 4 4 2
3 4 4 4 3 5 5 5 5 5 5 3
4 5
As a tetrangle, the first four triangles are:
{1}
{2},{1,2}
{3},{1,3},{2,3},{1,2,3}
{4},{1,4},{2,4},{3,4},{1,2,4},{1,3,4},{2,3,4},{1,2,3,4}
MATHEMATICA
SortBy[Rest[Subsets[Range[5]]], Last]
CROSSREFS
Triangle lengths are A000079.
Triangle sums are A001793.
Positions of first appearances are A005183.
Set maxima are A070939.
Set lengths are A124736.
Partition/composition orderings: A026791, A026792, A026793, A036036, A036037, A048793, A066099, A080577, A112798, A118457, A124734, A162247, A193073, A211992, A228100, A228531, A246688, A272020, A296774, A299755, A304038, A319247, A329631, A334301, A334302, A334439, A334442, A335122, A344085, A344086, A344087, A344088, A344089.
KEYWORD
nonn,tabf
AUTHOR
Gus Wiseman, May 11 2021
STATUS
approved