%I #3 Apr 28 2014 12:05:46
%S 1,1,2,9,49,322,2411,19868,178832,1724689,17728545,192634930,
%T 2201760840,26341552085,328644606302,4261866683006,57288746422850,
%U 796337785825197,11422744246417607,168765251734898485,2564015637845130072,39998356172536082076,639840751503820832346
%N Number of standard Young tableaux with 2n cells and exactly n successions.
%C A succession is a pair of cells (v, v+1) lying in the same row.
%C Also number of ballot sequences of length 2n having exactly n flat steps.
%F a(n) = A238125(2n,n).
%K nonn
%O 0,3
%A _Joerg Arndt_ and _Alois P. Heinz_, Apr 28 2014