import math

def are_coprime(a, b):
    return math.gcd(a, b) == 1

def find_greatest():
    input()
    alist = [int(a) for a in input().split()]

    mapping = {}
    for i in range(len(alist)):
        mapping[alist[i]] = i

    maxi = -1
    for a in mapping:
        for b in mapping:
            if mapping[a]+mapping[b]+2 > maxi and are_coprime(a, b):
                maxi = mapping[a]+mapping[b]+2

    return maxi

def main():
    nb = int(input())
    for i in range(nb):
        print(find_greatest())

main()