A181948 Triangle read by rows: T(n,k) (2 <= k <= n) = dimension of partially ordered set of all 1-element and (k-1)-element subsets of an n-set.

2, 2, 3, 2, 3, 4, 2, 4, 4, 5, 2, 4, 5, 5, 6, 2, 4, 6, 6, 6, 7, 2, 4, 6, 7, 7, 7, 8, 2, 4, 6, 8, 8, 8, 8, 9, 2, 4, 6, 8, 9, 9, 9, 9, 10, 2, 4, 7, 9, 10, 10, 10, 10, 10, 11, 2, 4, 7, 9, 10, 11, 11, 11, 11, 11, 12, 2, 5, 7, 9, 11, 12, 12, 12, 12, 12, 12, 13, 2, 5, 7, 9, 12, 12, 13, 13, 13, 13, 13, 13, 14

Offset

2,1

References

Trotter, William T., Jr. Some combinatorial problems for permutations. Proceedings of the Eighth Southeastern Conference on Combinatorics, Graph Theory and Computing (Louisiana State Univ., Baton Rouge, La., 1977), pp. 619--632. Congressus Numerantium, No. XIX, Utilitas Math., Winnipeg, Man., 1977. MR0480110 (58 #309).

Links

Table of n, a(n) for n=2..92.

Example

Triangle begins:
2
2 3
2 3 4
2 4 4 5
2 4 5 5 6
2 4 6 6 6 7
2 4 6 7 7 7 8
2 4 6 8 8 8 8 9
2 4 6 8 9 9 9 9 10
2 4 7 9 10 10 10 10 10 11
2 4 7 9 10 11 11 11 11 11 12
2 5 7 9 11 12 12 12 12 12 12 13
2 5 7 9 12 12 13 13 13 13 13 13 14...

Crossrefs

Sequence in context: A221999 A222334 A340716 * A238943 A070081 A366686

Adjacent sequences: A181945 A181946 A181947 * A181949 A181950 A181951

Keyword

nonn,tabl

Author

N. J. A. Sloane, Apr 03 2012

Status

approved