write a go solution for Description:
You are given an array a of n numbers. There are also q queries of the form s,d,k.

For each query q, find the sum of elements a_s+a_s+d*2+...+a_s+d*(k-1)*k. In other words, for each query, it is necessary to find the sum of k elements of the array with indices starting from the s-th, taking steps of size d, multiplying it by the serial number of the element in the resulting sequence.

Input Format:
Each test consists of several testcases. The first line contains one integer t (1<=t<=10^4) — the number of testcases. Next lines contain descriptions of testcases.

The first line of each testcase contains two numbers n,q (1<=n<=10^5,1<=q<=2*10^5) — the number of elements in the array a and the number of queries.

The second line contains n integers a_1,...a_n (-10^8<=a_1,...,a_n<=10^8) — elements of the array a.

The next q lines each contain three integers s, d, and k (1<=s,d,k<=n, s+d*(k-1)<=n ).

It is guaranteed that the sum of n over all testcases does not exceed 10^5, and that the sum of q over all testcases does not exceed 2*10^5.

Output Format:
For each testcase, print q numbers in a separate line — the desired sums, separated with space.

Note:
None. Output only the code with no comments, explanation, or additional text.