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.

Examples

Construct a series manually:

SeriesData[x, 0, {1, 1, 1/2, 1/6}, 0, 4, 1]
(* 1 + x + x^2/2 + x^3/6 + O[x]^4 *)

Extract series data:

s = Series[Sin[x], {x, 0, 3}];
SeriesData[s]

Please visit the official Wolfram Language Reference for more details.