%I #13 Jul 30 2017 22:57:44
%S 1,1,2,2,3,5,6,7,16,21,26,64,63,125,276
%N Number of nonisomorphic circulant oriented graphs (i.e., Cayley graphs for the cyclic group) of order n.
%C These and subsequent values for (twice) squarefree and (twice) prime-squared orders can be found in the Liskovets reference.
%C I am unable to reproduce these results except most notably for n prime or prime squared. If anyone is able to get a(8)=7 it would be appreciated if you could let me know how or add an example. For a(8), I initially get 10 distinct step sets (up to Cayley isomorphism) which reduce to 9 after graph isomorphism testing but that is still too high. The step sets I have are {}, {1}, {2}, {1,2}, {1,-2}, {1,3}, {1,-3}, {1,2,3}, {1,2,-3}, {1,-2,-3}. After constructing the circulant graphs and testing for isomorphisms {1,2,-3} and {1,-2,-3} combine into a single class. Note that a step of 4 is not possible since this always violates the orientation requirement. Is there another way of looking at this problem, is there another kind of reduction or have I made a logical mistake? Other values I cannot reproduce include a(12) and a(15). - _Andrew Howroyd_, Apr 30 2017
%H V. A. Liskovets, <a href="https://arxiv.org/abs/math/0104131">Some identities for enumerators of circulant graphs</a>, arXiv:math/0104131 [math.CO], 2001.
%Y Cf. A049297, A056391, A283189.
%K nonn,more
%O 1,3
%A _Valery A. Liskovets_, May 09 2001