%I #5 Aug 15 2015 09:40:25
%S 1,3,20,56,576,1408,6656,5120,278528,622592,2752512,6029312,52428800,
%T 113246208,486539264,1040187392,11811160064,15032385536,317827579904,
%U 223338299392,5634997092352,11819749998592,3298534883328
%N Denominators of coefficient of x^(n+1/2) in the series expansion of the haversine.
%H Eric Weisstein's World of Mathematics, <a href="http://mathworld.wolfram.com/InverseHaversine.html">Inverse Haversine</a>
%e 2*sqrt(z) + z^(3/2)/3 + (3*z^(5/2))/20 + (5*z^(7/2))/56 + (35*z^(9/2))/576 + ...
%Y Cf. A143581.
%K nonn,frac
%O 1,2
%A _Eric W. Weisstein_, Aug 24 2008