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A273988
The number of slim, rectangular lattices of length n>=2.
2
1, 2, 6, 19, 78, 387, 2327, 16384, 132336, 1203145, 12146959, 134749221, 1628840129, 21308361378, 299940041508, 4520381905248, 72625922986869, 1239160455312246, 22377511072312218, 426411855436193451, 8550614540544797370, 179989316790109543775, 3968315581691624472787, 91451247683519227059456
OFFSET
2,2
COMMENTS
The initial term is the four element diamond shape lattice.
LINKS
Gábor Czédli, Tamás Dékány, Gergő Gyenizse, Júlia Kulin, The number of slim rectangular lattices, Algebra Universalis, 2016, Volume 75, Issue 1, pp 33-50
FORMULA
a(n) = 1/2*( A273596(n) + Sum_{k=1..floor(n/2)} binomial(n-k-1,k-1)*A000085(n-2k) ).
a(n) ~ exp(2) * n! / (2*n^2). - Vaclav Kotesovec, Jun 30 2016
CROSSREFS
Sequence in context: A008989 A057240 A079564 * A287897 A349401 A344317
KEYWORD
nonn
AUTHOR
Tamas Dekany, Jun 06 2016
STATUS
approved