#include<iostream>
#include<cstdio>
#include<cstring>
#include<cmath>
#define getchar() (*S++)
#define MN 100000
#define pi acos(-1)
#define ll long long
char B[1<<26],*S=B;
using namespace std;
int X;char ch;
inline int read()
{X = 0 , ch = getchar();while(ch < '0' || ch > '9') ch = getchar();while(ch >= '0' && ch <= '9'){X = X * 10 + ch - '0';ch = getchar();}return X;
}struct cp{double r,u;cp(double _r=0,double _u=0):r(_r),u(_u){}cp operator+(cp b){return cp(r+b.r,u+b.u);}cp operator-(cp b){return cp(r-b.r,u-b.u);}cp operator*(cp b){return cp(r*b.r-u*b.u,r*b.u+u*b.r);}cp operator/(double y){return cp(r/y,u/y);}
}w[2][MN],a[MN],b[MN];int n,s[MN+5],size,N;ll num1[MN],num2[MN];
ll ans=0;void init(int mx)
{w[0][0]=w[1][mx]=cp(1,0);w[0][1]=w[1][mx-1]=cp(cos(2*pi/mx),sin(2*pi/mx));for(int i=2;i<=mx;i++)w[0][i]=w[1][mx-i]=w[0][i-1]*w[0][1];
}void fft(cp*x,int b)
{for(register int i=0,j=0;i<N;++i){if(i>j)swap(x[i],x[j]);for(int k=N>>1;(j^=k)<k;k>>=1);}for(register int i=2;i<=N;i<<=1)for(register int j=0;j<N;j+=i)for(register int k=0;k<i>>1;k++){cp t=x[j+k+(i>>1)]*w[b][N/i*k];x[j+k+(i>>1)]=x[j+k]-t;x[j+k]=x[j+k]+t;}if(b)for(register int i=0;i<N;i++)x[i]=x[i]/N;
}int main()
{fread(B,1,1<<26,stdin);n=read();size=min(n,6*(int)sqrt(n));for(register int i=1;i<=n;++i)s[i]=read(),++num2[s[i]];for(register int i=1;i<n;i+=size){int r=min(i+size-1,n);for(register int j=i;j<=r;++j)--num2[s[j]];for(register int j=i;j<=r;++j){for(int k=j+1;k<=r;k++){int x=2*s[j]-s[k];if(x>=0)ans+=num1[x];x=2*s[k]-s[j];if(x>=0)ans+=num2[x];}++num1[s[j]];}}for(register int i=1;i<n;i+=size){int r=min(i+size-1,n),mx=0;for(register int j=1;j<i;++j)a[s[j]].r++,mx=max(mx,s[j]);for(register int j=r+1;j<=n;++j)b[s[j]].r++,mx=max(mx,s[j]);for(N=1;N<=mx;N<<=1);N<<=1;init(N);fft(a,0);fft(b,0);for(register int j=0;j<N;++j)a[j]=a[j]*b[j];fft(a,1);for(register int j=i;j<=r;++j) ans+=(ll)(a[s[j]<<1].r+0.5);memset(a,0,sizeof(cp)*N);memset(b,0,sizeof(cp)*N);}printf("%lld\n",ans);return 0;
}