Write a function that adds all the even numbers between 2 an
     Write a function that adds all the even numbers between 2 and 3^n, where n is a number passed to the faunction.   
  
  Solution
function y=sumnalleven(n)
 y=0;
 for i=2:3^n
 if rem(i,2)==0
 y=y+i;
 end
 end
RESULT:
>> sumnalleven(2)
ans =
20
>> sumnalleven(5)
ans =
14762

