sum the series in matlab

I am trying to sum the following function in matlab but with the following code I got "Undefined 'symsum' for input arguments of type 'double'. Any idea?

 p=3;

c=3;

r=4;

Syms v;

Syms r;

v=0; M= (r^c/factorial(c)*(1-p)+symsum(r^v/factorial(v),v, [v, c-1])^(-1));

Answer 1

[Azzi Abdelmalek]

p=3;
c=3;
r=4;
syms v 
M= (r^c/factorial(c)*(1-p)+symsum(r^v/factorial(v),v, [v, c-1])^(-1))

[Smith]

Thanks. I try to run this but still no value has shown for M. I used p=0.2 (as p<1). Any idea?