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%I #6 Apr 28 2014 19:01:47
%S 9,146,1324,8786,47013,214997,874413,3228005,11049817,35389760,
%T 107476721,310853113,863984856,2313084483,6003120701,15122836712,
%U 37154716734,89093938147,209258012995,481663102867,1089445474512,2422311605452,5305675093522,11451261202545
%N Number of ballot sequences of length n having exactly four descents.
%e a(8) = 9: [1,2,1,2,1,3,2,1], [1,2,1,3,1,4,2,1], [1,2,1,3,2,1,2,1], [1,2,1,3,2,1,3,1], [1,2,1,3,2,1,3,2], [1,2,1,3,2,1,4,1], [1,2,1,3,2,1,4,2], [1,2,1,3,2,1,4,3], [1,2,1,3,2,4,3,1].
%Y Column k=4 of A238121 and of A238122.
%K nonn
%O 8,1
%A _Joerg Arndt_ and _Alois P. Heinz_, Apr 28 2014
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