SeriesData

SeriesData[x,x0,{a0,a1,…},nmin,nmax,den] represents a power series in the variable x about the point x0. The ai are the coefficients in the power series. The powers of (x-x0) that appear are nmin/den, (nmin+1)/den, …, nmax/den. 

Please visit the official Wolfram Language Reference for more details and examples on core symbols.