%I #7 Sep 09 2017 12:48:19
%S 1,3,11,31,91,250,690,1863,5017,13389,35621,94354,249352,657421,
%T 1730685,4550031,11950963,31365810,82274126,215711947,565376593,
%U 1481448697,3881041065,10165822434,26624745964,69725071281,182583838181,478093234315,1251829592839
%N Number of symmetrically unique Dyck paths of semilength n and height three.
%H Alois P. Heinz, <a href="/A291887/b291887.txt">Table of n, a(n) for n = 3..1000</a>
%H <a href="/index/Rec#order_07">Index entries for linear recurrences with constant coefficients</a>, signature (6, 9, 8, 27, 10, 10, 4).
%F G.f.: x^3*(x^4+2*x^23*x+1)/((2*x1)*(x^23*x+1)*(2*x^21)*(x^2+x1)).
%Y Column k=3 of A291883.
%K nonn,easy
%O 3,2
%A _Alois P. Heinz_, Sep 05 2017
