AHSME 1969 Problem 32

Let a sequence $\{u_n\}$ be defined by $u_1=5$ and the relationship $u_{n+1}-u_n=3+4(n-1), n=1,2,3\cdots.$If $u_n$ is expressed as a polynomial in $n$, the algebraic sum of its coefficients is: $\text{(A) 3} \text{(B) 4} \text{(C) 5} \text{(D) 6} \text{(E) 11}$