%I #8 May 05 2024 08:43:44
%S 4,36,1240,73240,7171176,1016813448,198480110880,50752206180576,
%T 16460660622560680,6595414427636900536,3198428240666246044704,
%U 1845848150787599809368856,1250049326783769438348496480,981653074459964543314138858320
%N Number of 2*n-sided cycles with the property that one makes the same number of left and right turns while following its edges.
%C Cycles that differ by rotation or reflection are counted separately. By "n-sided cycles" we mean the cycles that can be drawn by connecting n equally spaced points on a circle (possibly self-intersecting).
%H Ludovic Schwob, <a href="/A371611/a371611.pdf">Illustration of a(3)</a>
%F a(n) is always divisible by 2*n, because the considered cycles cannot have rotational symmetry.
%Y Cf. A365094, A295264,
%K nonn
%O 2,1
%A _Ludovic Schwob_, Mar 29 2024