increase good prefixes in the permutation

# cook your dish here
# https://www.codechef.com/problems/PREPER?tab=statement
def check(sum,i):
    return sum == ((i*(i+1))//2)# a permutation pref is good if its sum is matching with sum of N natural numbers that means all numbers are present none are missing
def maxSubArrSum(p):
    maxi = float('-inf')
    currMax = 0
    for ele in p:
        currMax += ele
        if currMax > maxi:
            maxi = currMax
        if currMax < 0:
            currMax = 0#resetting

    return maxi



def getMaxGoodPrefs(arr):
    #let g be the current good prefixes
    g = 0
    sum = 0
    for i in range(len(arr)):
        sum += arr[i]
        if check(sum,i+1):
            g += 1

    '''

    now you have 2 ways to swap
    important thing is no matter what L and R you choose
    only adjacent elements will be swapped

    which is odd even swapping
    and even odd swapping
    we need to perform 2 ways and check the max possible

    and also our aim is to enhance g not to ruin it

    '''
    #include first element and check 2 steps
    #if they swapped and not swapped
    sumf = 0
    poe = []
    n = len(arr)
    for i in range(0,n,2):
        gnotswap = 0
        gswap = 0
        if i+1<n:
            #if not swap
            if check(sumf+arr[i],i+1):
                gnotswap += 1
            #for next position arr[i] needs to be included
            sumf += arr[i]
            if check(sumf+arr[i+1],i+2):
                gnotswap += 1
            sumf -= arr[i] #nullifying after check

            #if swapped that means arr[i+1] is the first element in this pair

            if check(sumf+arr[i+1],i+1):
                gswap += 1
            #for next position arr[i+1] needs to be included
            sumf += arr[i+1]
            if check(sumf+arr[i],i+2):
                gswap += 1
            sumf -= arr[i+1] #nullifying after check

            sumf += arr[i] + arr[i+1]#preparing for next pair
            diff = gswap-gnotswap
            poe.append(diff)

    sumse = arr[0] #as we are not touching for changing
    peo = []
    for i in range(1,n,2):
        gnotswap = 0
        gswap = 0
        if i+1<n:
            #if not swap
            if check(sumse+arr[i],i+1):
                gnotswap += 1
            #for next position arr[i] needs to be included
            sumse += arr[i]
            if check(sumse+arr[i+1],i+2):
                gnotswap += 1
            sumse -= arr[i] #nullifying after check

            #if swapped that means arr[i+1] is the first element in this pair

            if check(sumse+arr[i+1],i+1):
                gswap += 1
            #for next position arr[i+1] needs to be included
            sumse += arr[i+1]
            if check(sumse+arr[i],i+2):
                gswap += 1
            sumse -= arr[i+1] #nullifying after check

            sumse += arr[i] + arr[i+1]#preparing for next pair

            diff = gswap-gnotswap
            peo.append(diff)

    max1 = maxSubArrSum(poe)
    max2 = maxSubArrSum(peo)
    maxChangedG = max(0,max1,max2)
    return g+maxChangedG



def main():
    tc = int(input())
    for i in range(tc):
        n = int(input())
        arr = list(map(int,input().split()))
        curr = getMaxGoodPrefs(arr)
        print(curr)

main()