Double covering of the Painlev\'e I equation and its singular analysis

In this note, we will do analysis of accessible singular points for a polynomial Hamiltonian system obtained by taking a double covering of the Painlev\'e I equation. We will show that this system passes the Painlev\'e $\alpha$-test for all accessible singular points $P_i \ (i=1,2,3)$. We note its holomorphy condition of the first Painlev\'e system.