Series[Tan[x], {x, 0, 20}]

(∑_(k = 1)^10)(((((-1))^(k + 1)) (2^(2  
                      k)) ((2^(2  k)) - 1))/((2  k)!)) 
          BernoulliB[2  k] (x^(2  k - 1)) + O[x]^21

(∑_(k = 1)^∞)(((((-1))^(k + 1)) (2^(2  
                      k)) ((2^(2  k)) - 1))/((2  k)!)) 
          BernoulliB[2  k] (x^(2  k - 1)) + O[x]^21

Series[(x/((E^x) - 1)), {x, 0, 20}]

(∑_(k = 0)^20) BernoulliB[k]/(k!) (x^k) + 
      O[x]^21

(∑_(k = 0)^∞) BernoulliB[k]/(k!) (x^k) + 
      O[x]^21

(∑_(k = 0)^∞) ((x^k)/(k!))

(∑_(k = 0)^∞)((((-1))^k)/((2  k + 1)!)) 
        (x^(2  k + 1))

Needs["SpecialFunctions`"]

FPS[(E^x), x]

FPS[Sin[x], x]

FPS[Cos[x], x]

s = FPS[(E^((Sqrt[x]))), x]

s /. {sum -> Sum}

specfunprint
Clear[f]

FPS[(E^x), x]

FPS[(E^((Sqrt[x]))), x]

specfunprintoff