OFFSET
1,4
COMMENTS
A graph is regular if all vertices have the same degree.
LINKS
MATHEMATICA
csm[s_]:=With[{c=Select[Tuples[Range[Length[s]], 2], And[OrderedQ[#], UnsameQ@@#, Length[Intersection@@s[[#]]]>0]&]}, If[c=={}, s, csm[Sort[Append[Delete[s, List/@c[[1]]], Union@@s[[c[[1]]]]]]]]];
Table[If[n==1, 1, Length[Select[Subsets[Subsets[Range[n], {2}]], And[Union@@#==Range[n], SameQ@@Length/@Split[Sort[Join@@#]], Length[csm[#]]==1]&]]], {n, 6}]
CROSSREFS
KEYWORD
nonn
AUTHOR
Gus Wiseman, Dec 22 2018
EXTENSIONS
a(8)-a(15) from Andrew Howroyd, Dec 23 2018
a(16)-a(18) from Andrew Howroyd, Sep 02 2019
STATUS
approved