// includes
#include <bits/stdc++.h>
using namespace std;

// macros
#define pb emplace_back
#define mk make_pair
#define FOR(i, a, b) for(int i=(a);i<(b);++i)
#define rep(i, n) FOR(i, 0, n)
#define rrep(i, n) for(int i=((int)(n)-1);i>=0;i--)
#define irep(itr, st) for(auto itr = (st).begin(); itr != (st).end(); ++itr)
#define irrep(itr, st) for(auto itr = (st).rbegin(); itr != (st).rend(); ++itr)
#define whole(x) (x).begin(),(x).end()
#define sz(x) ((int)(x).size())
#define UNIQUE(v) v.erase(unique(v.begin(), v.end()), v.end())
#define bit(n) (1LL<<(n))
// functions
template <class T>bool chmax(T &a, const T &b){if(a < b){a = b; return 1;} return 0;}
template <class T>bool chmin(T &a, const T &b){if(a > b){a = b; return 1;} return 0;}
template <typename T> istream &operator>>(istream &is, vector<T> &vec){for(auto &v: vec)is >> v; return is;}
template <typename T> ostream &operator<<(ostream &os, const vector<T>& vec){for(int i = 0; i < vec.size(); i++){ os << vec[i]; if(i + 1 != vec.size())os << " ";} return os;}
template <typename T> ostream &operator<<(ostream &os, const set<T>& st){for(auto itr = st.begin(); itr != st.end(); ++itr){ os << *itr; auto titr = itr; if(++titr != st.end())os << " ";} return os;}
template <typename T> ostream &operator<<(ostream &os, const unordered_set<T>& st){for(auto itr = st.begin(); itr != st.end(); ++itr){ os << *itr; auto titr = itr; if(++titr != st.end())os << " ";} return os;}
template <typename T> ostream &operator<<(ostream &os, const multiset<T>& st){for(auto itr = st.begin(); itr != st.end(); ++itr){ os << *itr; auto titr = itr; if(++titr != st.end())os << " ";} return os;}
template <typename T> ostream &operator<<(ostream &os, const unordered_multiset<T>& st){for(auto itr = st.begin(); itr != st.end(); ++itr){ os << *itr; auto titr = itr; if(++titr != st.end())os << " ";} return os;}
template <typename T1, typename T2> ostream &operator<<(ostream &os, const pair<T1, T2> &p){os << p.first << " " << p.second; return os;}
template <typename T1, typename T2> ostream &operator<<(ostream &os, const map<T1, T2> &mp){for(auto itr = mp.begin(); itr != mp.end(); ++itr){ os << itr->first << ":" << itr->second; auto titr = itr; if(++titr != mp.end())os << " "; } return os;}
template <typename T1, typename T2> ostream &operator<<(ostream &os, const unordered_map<T1, T2> &mp){for(auto itr = mp.begin(); itr != mp.end(); ++itr){ os << itr->first << ":" << itr->second; auto titr = itr; if(++titr != mp.end())os << " "; } return os;}
//  types
using ll = long long int;
using P = pair<int, int>;
// constants
const int inf = 1e9;
const ll linf = 1LL << 50;
const double EPS = 1e-10;
const int mod = 1000000007;
const int dx[4] = {-1, 0, 1, 0};
const int dy[4] = {0, -1, 0, 1};
// io
struct fast_io{
  fast_io(){ios_base::sync_with_stdio(false); cin.tie(0); cout << fixed << setprecision(20);}
} fast_io_;

template <typename T>
T power(T a, T n, T mod) {
  T res = 1;
  T tmp = n;
  T curr = a;
  while(tmp){
    if(tmp % 2 == 1){
      res = (T)(res * curr % mod);
    }
    curr = (T)(curr * curr % mod);
    tmp >>= 1;
  }

  return res;
}

vector<int> child[200010];
int h[200010];

void dfs(int i){
  for(auto e: child[i]){
    h[e] = h[i] + 1;
    dfs(e);
  }
}

struct D{
  ll dp[3];
  D(ll x0, ll x1, ll x2){
    dp[0] = x0;
    dp[1] = x1;
    dp[2] = x2;
  }
  void merge(const D& r){
    ll x0 = dp[0], x1 = dp[1], x2 = dp[2];
    dp[0] = x0 * r.dp[0] % mod;
    dp[1] = (x0 * r.dp[1] % mod + x1 * r.dp[0] % mod) % mod;
    dp[2] = (x2 * (r.dp[0] + r.dp[1] + r.dp[2]) % mod + x1 * (r.dp[1] + r.dp[2]) % mod + x0 * r.dp[2] % mod) % mod;
  }
};

deque<D> vd[200010];
void calc(int i){
  for(auto e: child[i])calc(e);
  if(sz(child[i]) == 0){
    vd[i].push_front(D(1, 1, 0));
    return;
  }
  swap(vd[i], vd[child[i][0]]);
  int max_depth = 0;
  for(int j = 1; j < sz(child[i]); j++){
    if(sz(vd[child[i][j]]) > sz(vd[i])){
      swap(vd[i], vd[child[i][j]]);
    }
    for(int k = 0; k < sz(vd[child[i][j]]); k++){
      vd[i][k].merge(vd[child[i][j]][k]);
    }
    max_depth = max(max_depth, sz(vd[child[i][j]]));
  }
  for(int k = 0; k < max_depth; k++){
    vd[i][k].dp[0] += vd[i][k].dp[2];
    vd[i][k].dp[2] = 0;
  }
  vd[i].push_front(D(1, 1, 0));
}

int main(int argc, char const* argv[])
{
  int n; cin >> n;
  rep(i, n){
    int p; cin >> p;
    child[p].pb(i + 1);
  }
  dfs(0);
  vector<int> hcnt(n + 1, 0); rep(i, n + 1)hcnt[h[i]]++;
  calc(0);
  ll res = 0;
  rep(i, sz(vd[0])){
    ll val = vd[0][i].dp[1];
    res = (res + val * power<ll>(2, n + 1 - hcnt[i], mod) % mod) % mod;
  }
  cout << res << endl;
  return 0;
}


Measured memory_bytes: 238580