Question: SnowFlake problem (formula)

Hey guys. Can you help me with this problem? I'm trying to plug in a snowflake equation in finding the perimeter of a snowflake on the nth step. The function is as follows:

 

p:=n->(3*(3/4)^k, k=1..n);
I'm trying to find the limit of this equation and it's suppose to give me infinity by using this command:
limit(pn(n), n=infinity);     but it's not quite giving me the limit. The limit is suppose to be infinity. Any help would be
appreciated. 
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