935 B | 935 chars
import sys
from math import sqrt, pi, sin, factorial, ceil, floor
from datetime import datetime, timedelta
SYS_INPUT = True
RECURSION_LIMIT = 10 ** 7
SET_RECURSION = False
BLANK = " "
if SET_RECURSION:
sys.setrecursionlimit(RECURSION_LIMIT)
inp = lambda : sys.stdin.readline().rstrip() if SYS_INPUT else input()
mii = lambda x = BLANK : [*map(int,inp().split(x))]
mfi = lambda x = BLANK : [*map(float,inp().split(x))]
ii = lambda : int(inp())
fi = lambda : float(inp())
isplit = lambda : inp().split()
p = print
def gcd(a, b): return gcd(b, a % b) if b > 0 else a
def lcm(a, b): return a * b // gcd(a, b)
def solve():
n = ii()
l = sorted(mii())
d = {}
for i in l:
d[i] = True
ans = 0
for i in range(n):
for j in range(i + 1, n):
diff = l[j] - l[i]
c = l[j] + diff
if d.get(c, False):
ans += 1
p(ans)
if __name__ == "__main__":
tc = ii()
for t in range(1, tc+1):
ret = solve()