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%I #7 Apr 28 2014 19:00:24
%S 1,5,16,43,99,215,430,834,1529,2765,4792,8216,13684,22575,36402,58285,
%T 91617,143097,220317,337100,509718,766655,1141457,1690994,2484138,
%U 3631902,5271297,7617750,10937657,15640771,22240250,31502316,44396662,62345539,87149572
%N Number of ballot sequences of length n having exactly one descent.
%e a(3) = 1: [1,2,1].
%e a(4) = 5: [1,1,2,1], [1,2,1,1], [1,2,1,2], [1,2,1,3], [1,2,3,1].
%Y Column k=1 of A238121 and of A238122.
%K nonn
%O 3,2
%A _Joerg Arndt_ and _Alois P. Heinz_, Apr 28 2014
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