%I #2 Apr 30 2014 01:31:04

%S 0,0,1,6,47,433,4826,63344,957206,16368226,312484331,6588211317,

%T 152035645781,3811750833515,103171389227156,2998418499414228,

%U 93127351040630156,3078376326065274609,107905191218919625781

%N [ (2n-1)!!/(4n) ].

%C Asymptotic estimate for A054499(n).

%H A. Khruzin, <a href="http://arXiv.org/abs/math.CO/0008209">Enumeration of chord diagrams</a>

%K nonn

%O 1,4

%A _Ralf Stephan_, Mar 02 2005