2 sequences : vertices and edges

[Yuval Dekel]

Let :
a(n) = minimal number of vertices in a graph that has automorphism group 
isomorphic to the cyclic group C_n ,

b(n) = minimal number of edges  in a graph that has automorphism group 
isomorphic to the cyclic group C_n .

If I am not mistaken I once saw a(n) in the OEIS but I can't find it now .

Does someone know the numbers a(n) and b(n) ? are both sequences in the OEIS 
?

Here is a related sequence :
http://www.research.att.com/projects/OEIS?Anum=A080803

Thanks,
Yuval

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