#include<iostream>
#include<cstdio>
using namespace std;
const int N=40005;
const int mod=998244353;
int a[N],f[N][N];
int main(){
	int n,i,j;
	int  ans=0;
	int p=20000;
	cin>>n;
	for(i=1;i<=n;++i)cin>>a[i];
	for(i=1;i<=n;++i){
		ans++;
		for(j=i-1;j>0;j--){
			f[i][a[i]-a[j]+p]+=f[j][a[i]-a[j]+p]+1;
			f[i][a[i]-a[j]+p]%=mod;
			ans+=f[j][a[i]-a[j]+p]+1;
			ans%=mod;
		}
	}
	cout<<ans;
	return 0;
}