A180962 Number of linear extensions for Young-Fibonacci lattices of increasing rank

1, 1, 2, 16, 4200, 1093025200

Offset

1,3

References

Donald E. Knuth, The Art of Computer Programming, Volume 4 Fascicle 2, Generating All Tuples and Permutations (2005), v+128pp. ISBN 0-201-85393-0. [Algorithm V for generating all topological sorts.]

Links

Table of n, a(n) for n=1..6.

Frank Ruskey, The Combinatorial Object Server (Implementation of Varol-Rotem algorithm).

Richard P. Stanley, Differential posets, Journal of the American Mathematical Society Vol. 1, No. 4, pp. 919-961, 1988.

Wikipedia, Young-Fibonacci lattice

Example

For n = 3, the Young-Fibonacci lattice as defined by the following edge set {(1,2),(2,3),(2,4)} has two total orderings: 1234 and 1243. The sequence increases rapidly since Young-Fibonacci lattices are sparse digraphs.

Crossrefs

Sequence in context: A138834 A088321 A061301 * A324565 A306729 A325049

Adjacent sequences: A180959 A180960 A180961 * A180963 A180964 A180965

Keyword

nonn,hard,more

Author

Nikolaos Kavvadias, Jan 23 2011

Status

approved