Any idea how to draw this Feynman diagram?

Not sure if this is a Feynman integral.

documentclass[tikz,border=3mm]{standalone}
begin{document}
begin{tikzpicture}[declare function={a=1.2;b=1.5;}]
 draw[teal,dashed,rotate=-22.5] (90:a) foreach X in {45,0,...,-180}
 {-- (X:a) edge ++ (X:0.5)} -- (135:a);
 draw node[circle,fill,draw,inner sep=0.8ex](O){} 
   foreach X [count=Y] in {45,0,...,-225}
  {(X:b) node[circle,draw,thin,inner sep=0.5ex](pY){} edge[very thick] (O)};
 path foreach X [count=Y from 2] in {n-1,n,1,2,3} 
 {(pY) to[edge label={$a_{X}$}] (O)};
end{tikzpicture}
end{document}