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Number of linear extensions of the one-level grid poset G[(3^n), (0^(n-1)), (0^(n-1))].
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%I #13 Dec 15 2016 18:10:40

%S 1,70,26599,29609650,72574079902,332014782982540,2545213373338499072,

%T 30302687687176712355840,529556871638491591748878336,

%U 13004213964445490176628310933504,433440210434110194677894532074307584

%N Number of linear extensions of the one-level grid poset G[(3^n), (0^(n-1)), (0^(n-1))].

%C The definition of a one-level grid poset can be found in the Pan links. The number of linear extensions of one-level grid poset G[(0^n), (0^(n-1)), (0^(n-1))] is given by Catalan number A000108(n), the number of linear extensions of the one-level grid poset G[(1^n), (0^(n-1)), (0^(n-1))] is given by A274644(n) and number of linear extensions of the one-level grid poset G[(2^n), (0^(n-1)), (0^(n-1))] is given by A274645(n).

%H Ran Pan, <a href="http://www.math.ucsd.edu/~projectp/problems/p1.html">Problem 1</a>, Project P.

%H Ran Pan, <a href="http://www.math.ucsd.edu/~projectp/problems/solutions/OneLevelGridPoset.pdf">Algorithmic Solution to Problem 1 (and linear extensions of general one-level grid-like posets)</a>, Project P.

%Y Cf. A000108, A274644, A274645.

%K nonn

%O 1,2

%A _Ran Pan_, Jun 30 2016