1/6 + 2/(9*x) - x/6 - (2*x^2)/9 + (1/3 + x/3)*HPL[{0}, x] + 
 ep*(1/6 + 2/(9*x) - x/6 - (2*x^2)/9 + (1/3 + x/3)*HPL[{0}, x]) + 
 ep^2*(1/6 + 2/(9*x) - x/6 - (2*x^2)/9 + (1/3 + x/3)*HPL[{0}, x]) + 
 ep^3*(1/6 + 2/(9*x) - x/6 - (2*x^2)/9 + (1/3 + x/3)*HPL[{0}, x])
