//Create Time: 2018-05-05 00:01:24
#include <iostream>
#include <cstdio>
#include <cstring>
#include <string>
#include <cmath>
#include <algorithm>
#include <vector>
#include <cstdlib>
#include <sstream>
#include <fstream>
#include <functional>
#include <list>
#include <deque>
#include <queue>
#include <stack>
#include <map>
#include <set>
#include <bitset>
#include <cctype>
#include <ctime>
#include <utility>
#include <complex>
#include <cassert>
#include <climits>
#include <iterator>
#include <tuple>
using namespace std;
#define snuke(i,x) for (__typeof((x).begin()) i = (x).begin(); i != (x).end(); ++i)
#define rep(i,a,n) for (int i=(a);i<(n);i++)
#define per(i,n,a) for (int i=(n)-1;i>=(a);i--)
// #define OUT(x) std::cout<<(#x)<<":"<<(x)<<std::endl
// #define TST(x) std::cout<<(#x)<<":"<<(x)<<" "
#define OUT(args...) {string _s=#args;replace(_s.begin(),_s.end(),',',' ');stringstream _ss(_s);istream_iterator<string> _it(_ss);OUT_TST("\n",_it,args);}
#define TST(args...) {string _s=#args;replace(_s.begin(),_s.end(),',',' ');stringstream _ss(_s);istream_iterator<string> _it(_ss);OUT_TST("",_it,args);}
#define SZ(v) ((int)(v).size())
#define all(v) (v).begin(), (v).end()
#define unq(x) sort(all(x)),(x).erase(unique(all(x)),(x).end())
#define mem(f,x) memset((f), (x), sizeof(f))
#define clr(f) mem(f,0)
#define x first
#define y second
#define mp make_pair
#define pb push_back
#define mt make_tuple
#define eb emplace_back
#define DEBUG
void OUT_TST(string s,istream_iterator<string> it) {cerr<<s;}
template<typename T, typename... Args> void OUT_TST(string s,istream_iterator<string> it,T a,Args... args){cerr<<*it<<"="<<a<<" ";OUT_TST(s,++it,args...);}
template<class T> void rd(T&ret){ret=0;bool ok=0,u=0;for(;;){int c=getchar();if(c>='0'&&c<='9')ret=(ret<<3)+(ret<<1)+c-'0',ok=1;else if(c=='-')u=1;else if(ok){if(u)ret*=-1;return;}}}
long long powmod(long long p,long long n,long long mod){long long ret=1;for(;n;n>>=1){if(n&1)ret=ret*p%mod;p=p*p%mod;}return ret;}
template <class T> bool chmin(T& a, const T &b) {return b < a? a = b, 1: 0;}
template <class T> bool chmax(T& a, const T &b) {return b > a? a = b, 1: 0;}
int gcd(int a,int b){return b?gcd(b,a%b):a;}
typedef long long ll;
typedef pair<int, int> pii;
typedef vector<int> vi;
typedef vector<pii > vii;
typedef tuple<int,int,int> tp;
/****head****/
const int N=(int)2e5+9;
const ll mod=(ll)1e9+7;
deque<tp> *dp[N],mem[N];
int n,len[N];
ll itwo;
vi eg[N];
bool cmp(int x,int y){
    return len[x]<len[y];
}
tp merge(tp &a,tp &b,bool fg){
    int s0,s1,s2,a0,a1,a2,b0,b1,b2;
    tie(a0,a1,a2)=a;
    tie(b0,b1,b2)=b;
    s1=((ll)a0*b1+(ll)a1*b0)%mod;
    s0=(ll)a0*b0%mod;
    s2=(1ll+mod*2ll-s0-s1)%mod;
    if(fg){
        s0+=s2;if(s0>=mod)s0-=mod;
        s2=0;
    }
    return tp{s0,s1,s2};
}
void dfs(int u){
    len[u]=0;
    for(int v:eg[u]){
        dfs(v);
        chmax(len[u],len[v]+1);
    }
    sort(all(eg[u]),cmp);
    rep(i,0,SZ(eg[u])-1){
        for(auto j=dp[eg[u][i]]->begin(),k=dp[eg[u][i+1]]->begin();j!=dp[eg[u][i]]->end();++j,++k){
            *k=merge(*j,*k,i==SZ(eg[u])-2);
        }
    }
    if(len[u]==0) dp[u]=&mem[u];
    else dp[u]=dp[eg[u].back()];
    // for(auto i=dp[u]->begin();i!=dp[u]->end();++i){
        // int a,b,c;tie(a,b,c)=*i;
        // a+=c;if(a>=mod)a-=mod;
        // c=0;
        // *i=tp{a,b,c};
    // }
    dp[u]->push_front(tp{itwo,itwo,0});
    // OUT(u);
    // int d=0;
    // snuke(it,*dp[u]){
        // OUT(d++,get<0>(*it),get<1>(*it),get<2>(*it));
    // }
}
int main(){
    itwo=powmod(2,mod-2,mod);
    cin>>n;++n;
    rep(i,0,n-1){
        int t;scanf("%d",&t);
        eg[t].pb(i+1);
    }
    dfs(0);
    ll ans=0,t=powmod(2,n,mod);
    // OUT(itwo,t);
    snuke(it,*dp[0]){
        // OUT(get<1>(*it),get<1>(*it)*t);
        ans+=get<1>(*it)*t%mod;
    }
    ans%=mod;
    if(ans<0)ans+=mod;
    cout<<ans<<endl;
    return 0;
}


Measured memory_bytes: 239348