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%I #13 Nov 25 2018 08:13:46
%S 1,3,12,54,232
%N Number of permutations of 1,2,...,2n+1 obtainable via labeled chip-firing.
%C It is conjectured that the permutations counted by a(n) have at most n inversions.
%H S. Hopkins, T. McConville, and J. Propp, <a href="https://arxiv.org/abs/1612.06816">Sorting via chip-firing</a>, arXiv: 1612.06816 [math.CO], 2017.
%H S. Hopkins, T. McConville, and J. Propp, <a href="http://www.combinatorics.org/ojs/index.php/eljc/article/view/v24i3p13">Sorting via chip-firing</a>, Electronic Journal of Combinatorics, 24, (2017), #P3.13.
%e For n=1 the a(1)=3 permutations are 123, 132, and 213.
%K nonn,more
%O 0,2
%A _James Propp_, Feb 24 2017