Computes the matrix exponential of this matrix, using the Padé approximant.
Uses the formula: e^A ≈ (1 + A/2 + A²/9 + A³/72 + A⁴/1008 + A⁵/30240) / (1 - A/2 + A²/9 - A³/72 + A⁴/1008 - A⁵/30240)
The matrix exponential of this matrix.