tests = int(input())

def pow(a, p):
    result = 1
    while p > 0:
        if p & 1 == 1:
            result *= a
            result %= 998244353
        p >>= 1 
        a = a * a % 998244353
    return result

def inv(a):
    return pow(a, 998244351)

for _ in range(tests):
    n = int(input())
    a = map(int, input().split())
    current = 0

    for ai in a:
        current = (current + ai + current * ai) % 998244353

    print(current)