Determine the argument of the table such that two tables have the same value

Suppose i have

A:=Plus @@ Table[2 (Pi/n) (i + 4), {i, 0, n/2, 1}]
B:=Plus @@ Table[ x , {i, (Pi/n), (n/2 + 1) (Pi/n), (Pi/n)}]

i need to determine the argument of the table on B, such that A=B for every $nin{2k|kinmathbb N}$ (even numbers).

My attempt:
I’m thinking about this summation:
$$sum_{i=0}^{n/2}frac{2pi}{n}(i+4)=sum_{i=1}^{n/2 +1}frac{2pi}{n}((i-1)+4)=sum_{i=1}^{n/2 +1}frac{2pi}{n}(i+3)$$
So, i got x=2(i+3). But when i test n=20, the results were different. Please help me. Thanks in advance.

N.B. If there’s something unclear about my question please tell me, i will edit it asap when i get the notification. Thanks.

a = Sum[2 (Pi/n) (i + 4), {i, 0, n/2, 1}];
b = Sum[x, {i, (Pi/n), (n/2 + 1) (Pi/n), (Pi/n)}];
FullSimplify[a == b, Assumptions -> n/2 ∈ PositiveIntegers]