Their are 36 terms.
f(1) is 11.
f(36) is 151.
f(2)=11+x
f(35)=151-x
The key to solving this is to make pairs by adding the first term and the 36th term. The 2nd term and the 35 term and so on. They pairs all equal 162 and their are 18 pairs or 36/2 pairs. 18*162=2916.