description: Let's call a sequence of integers x_1, x_2, ..., x_k MEX-correct if for all i (1 ≤ i ≤ k) |x_i - \operatorname{MEX}(x_1, x_2, ..., x_i)| ≤ 1 holds. Where \operatorname{MEX}(x_1, ..., x_k) is the minimum non-negative integer that doesn't belong to the set x_1, ..., x_k. For example, \operatorname{MEX}(1, 0, 1, 3) = 2 and \operatorname{MEX}(2, 1, 5) = 0.
  
  You are given an array a consisting of n non-negative integers. Calculate the number of non-empty MEX-correct subsequences of a given array. The number of subsequences can be very large, so print it modulo 998244353. 
  
  Note: a subsequence of an array a is a sequence [a_{i_1}, a_{i_2}, ..., a_{i_m}] meeting the constraints 1 ≤ i_1 < i_2 < ... < i_m ≤ n. If two different ways to choose the sequence of indices [i_1, i_2, ..., i_m] yield the same subsequence, the resulting subsequence should be counted twice (i. e. two subsequences are different if their sequences of indices [i_1, i_2, ..., i_m] are not the same).
  
  Input
  
  The first line contains a single integer t (1 ≤ t ≤ 10^5) — the number of test cases.
  
  The first line of each test case contains a single integer n (1 ≤ n ≤ 5 ⋅ 10^5).
  
  The second line contains n integers a_1, a_2, ..., a_n (0 ≤ a_i ≤ n).
  
  The sum of n over all test cases doesn't exceed 5 ⋅ 10^5.
  
  Output
  
  For each test case, print a single integer — the number of non-empty MEX-correct subsequences of a given array, taken modulo 998244353.
  
  Example
  
  Input
  
  
  4
  3
  0 2 1
  2
  1 0
  5
  0 0 0 0 0
  4
  0 1 2 3
  
  
  Output
  
  
  4
  2
  31
  7
  
  Note
  
  In the first example, the valid subsequences are [0], [1], [0,1] and [0,2].
  
  In the second example, the valid subsequences are [0] and [1].
  
  In the third example, any non-empty subsequence is valid. 
solution: import sys
  read=sys.stdin.buffer.read;readline=sys.stdin.buffer.readline;input=lambda:sys.stdin.readline().rstrip()
  import bisect,string,math,time,functools,random,fractions
  #from bisect import*
  #from heapq import heappush,heappop,heapify
  #from collections import deque,defaultdict,Counter
  #from itertools import permutations,combinations,groupby
  rep=range;R=range
  def I():return int(input())
  def LI():return [int(i) for i in input().split()]
  def SLI():return sorted([int(i) for i in input().split()])
  def LI_():return [int(i)-1 for i in input().split()]
  def S_():return input()
  def IS():return input().split()
  def LS():return [i for i in input().split()]
  def NI(n):return [int(input()) for i in range(n)]
  def NI_(n):return [int(input())-1 for i in range(n)]
  def NLI(n):return [[int(i) for i in input().split()] for i in range(n)]
  def NLI_(n):return [[int(i)-1 for i in input().split()] for i in range(n)]
  def StoLI():return [ord(i)-97 for i in input()]
  def ItoS(n):return chr(n+97)
  def LtoS(ls):return ''.join([chr(i+97) for i in ls])
  def RLI(n=8,a=1,b=10):return [random.randint(a,b)for i in range(n)]
  def RI(a=1,b=10):return random.randint(a,b)
  def INP():
      N=6
      n=random.randint(1,N)
      mn=0
      mx=n
      a=[random.randint(mn,mx) for i in range(n)]
      return n,a
  def Rtest(T):
      case,err=0,0
      for i in range(T):
          inp=INP()
          a1=naive(*inp)
          a2=solve(*inp)
          if a1!=a2:
              print(inp)
              print('naive',a1)
              print('solve',a2)
              err+=1
          case+=1
      print('Tested',case,'case with',err,'errors')
  def GI(V,E,ls=None,Directed=False,index=1):
      org_inp=[];g=[[] for i in range(V)]
      FromStdin=True if ls==None else False
      for i in range(E):
          if FromStdin:
              inp=LI()
              org_inp.append(inp)
          else:
              inp=ls[i]
          if len(inp)==2:a,b=inp;c=1
          else:a,b,c=inp
          if index==1:a-=1;b-=1
          aa=a;bb=b;g[a].append(bb)
          if not Directed:g[b].append(aa)
      return g,org_inp
  def RE(E):
      rt=[[]for i in range(len(E))]
      for i in range(len(E)):
          for nb,d in E[i]:
              rt[nb]+=(i,d),
      return rt
  def GGI(h,w,search=None,replacement_of_found='.',mp_def={'#':1,'.':0},boundary=1):
      #h,w,g,sg=GGI(h,w,search=['S','G'],replacement_of_found='.',mp_def={'#':1,'.':0},boundary=1) # sample usage
      mp=[boundary]*(w+2);found={}
      for i in R(h):
          s=input()
          for char in search:
              if char in s:
                  found[char]=((i+1)*(w+2)+s.index(char)+1)
                  mp_def[char]=mp_def[replacement_of_found]
          mp+=[boundary]+[mp_def[j] for j in s]+[boundary]
      mp+=[boundary]*(w+2)
      return h+2,w+2,mp,found
  def TI(n):return GI(n,n-1)
  def accum(ls):
      rt=[0]
      for i in ls:rt+=[rt[-1]+i]
      return rt
  def bit_combination(n,base=2):
      rt=[]
      for tb in R(base**n):s=[tb//(base**bt)%base for bt in R(n)];rt+=[s]
      return rt
  def gcd(x,y):
      if y==0:return x
      if x%y==0:return y
      while x%y!=0:x,y=y,x%y
      return y
  def YN(x):print(['NO','YES'][x])
  def Yn(x):print(['No','Yes'][x])
  def show(*inp,end='\n'):
      if show_flg:print(*inp,end=end)
  
  mo=10**9+7
  #mo=998244353
  inf=float('inf')
  FourNb=[(-1,0),(1,0),(0,1),(0,-1)];EightNb=[(-1,0),(1,0),(0,1),(0,-1),(1,1),(-1,-1),(1,-1),(-1,1)];compas=dict(zip('WENS',FourNb));cursol=dict(zip('LRUD',FourNb))
  alp=[chr(ord('a')+i)for i in range(26)]
  #sys.setrecursionlimit(10**7)
  
  
  show_flg=False
  show_flg=True
  
  ans=0
  
  mo=998244353 
  
  def mex(x):
      m=0
      for i in sorted(x):
          if i==m:
              m+=1
      return m
  
  def check(x):
      n=len(x)
      for i in range(n):
          if abs(x[i]-mex(x[:i+1]))>1:
              return False
      return True
  
  def naive(n,a):
      rt=0
      N=1<<n
      for i in range(1,N):
          s=[]
          for j in range(n):
              if i>>j&1:
                  s+=a[j],
          if check(s):
              rt+=1
      return rt
  
  def solve(n,a):
      d1=[0]*(n+3)
      d2=[0]*(n+3)
      
      for i in range(n):
          c=a[i]
          
          d1[c]+=d1[c]
          if c-1>=0:
              d1[c]+=d1[c-1]
          d1[c]%=mo
          
          if c-1>=0:
              d2[c-1]+=d2[c-1]
          if c-2>=0:
              d2[c-1]+=d1[c-2]
          d2[c+1]+=d2[c+1]
          d2[c]%=mo
          
          if c==0:
              d1[c]+=1
          if c==1:
              d2[0]+=1
          #show(d1,d2,c)
      return sum(d1)%mo+sum(d2)%mo
  
  for _ in range(I()):
      ans=0
      n=I()
      a=LI()
      
      d1=[0]*(n+3)
      d2=[0]*(n+3)
      
      for i in range(n):
          c=a[i]
          
          d1[c]+=d1[c]
          if c-1>=0:
              d1[c]+=d1[c-1]
          d1[c]%=mo
          
          if c-1>=0:
              d2[c-1]+=d2[c-1]
          if c-2>=0:
              d2[c-1]+=d1[c-2]
          d2[c+1]+=d2[c+1]
          d2[c]%=mo
          
          if c==0:
              d1[c]+=1
          if c==1:
              d2[0]+=1
          #show(d1,d2,c)
      ans=sum(d1)%mo+sum(d2)%mo
  
      #ans=solve(n,a)
      print(ans%mo)
  