OFFSET
0,1
COMMENTS
If you choose to adjoin a top and a bottom element to each resulting lattice, you must add 2 to these cardinalities: see A137400.
REFERENCES
G. Birkoff, Lattice Theory, American Mathematical Society, third edition (1967), pp. 63-64 [for the case n = 1].
LINKS
M. P. Schützenberger, Construction du treillis modulaire engendré par deux éléments et une chaine finie discrète, Comptes Rendus de lAcad. Sci. Paris, vol. 235 (1952), pp. 926-928.
K. Takeuchi, On free modular lattices II, Tohoku Mathematical Journal (2), vol. 11 (1959), pp. 1-12 [for the case n = 2].
EXAMPLE
When n = 0, the lattice consists of the two elements, their meet and their join, so a(0) = 4.
When n = 1, we get the free modular lattice generated by three elements, so a(1) = 28.
CROSSREFS
KEYWORD
nonn
AUTHOR
Lyle Ramshaw (lyle.ramshaw(AT)hp.com), Apr 08 2008
EXTENSIONS
More terms from Vladeta Jovovic, Feb 05 2010
STATUS
approved