For Lovelock gravity,
L=Rc2d2a2b2⋯Rcmdmambmδa2b2⋯ambmc2d2⋯cmdm
where
$$
\delta_{{jc_{1}d_{1}...c_{m}d_{m}}}^{{ia_{1}b_{1}...a_{m}b_{m}}}=\det\left[\begin{array}{c|ccc}\delta_{j}^{i} & \delta_{{c_{1}}}^{i} & \cdots & \delta_{{d_{m}}}^{i}\\hline \\delta_{j}^{{a{1}}}\\vdots & & \delta_{{c_{1}d_{1}...c_{m}d_{m}}}^{{a_{1}b_{1}...a_{m}b_{m}}}\\delta_{j}^{{b\{m}}}\end{array}\right]
$$
when m=2, we get Einstein gravity; when m=3, we get Gauss-Bonnet gravity. But how to deal with it more generally? More concretely, I don't know how to do it use for
loop.