#include <bits/stdc++.h>
using namespace std;
using lint = long long int;
using pint = pair<int, int>;
using plint = pair<lint, lint>;
struct fast_ios { fast_ios(){ cin.tie(0); ios::sync_with_stdio(false); cout << fixed << setprecision(20); }; } fast_ios_;
#define FOR(i, begin, end) for(int i=(begin),i##_end_=(end);i<i##_end_;i++)
#define IFOR(i, begin, end) for(int i=(end)-1,i##_begin_=(begin);i>=i##_begin_;i--)
#define REP(i, n) FOR(i,0,n)
#define IREP(i, n) IFOR(i,0,n)
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){ os << "["; for (auto v : vec) os << v << ","; os << "]"; return os; }
template<typename T> ostream& operator<<(ostream &os, const set<T> &vec){ os << "{"; for (auto v : vec) os << v << ","; os << "}"; return os; }
template<typename T> ostream& operator<<(ostream &os, const unordered_set<T> &vec){ os << "{"; for (auto v : vec) os << v << ","; os << "}"; return os; }
template<typename T> ostream& operator<<(ostream &os, const multiset<T> &vec){ os << "{"; for (auto v : vec) os << v << ","; os << "}"; return os; }
template<typename T> ostream& operator<<(ostream &os, const unordered_multiset<T> &vec){ os << "{"; for (auto v : vec) os << v << ","; os << "}"; return os; }
template<typename T1, typename T2> ostream& operator<<(ostream &os, const pair<T1, T2> &pa){ os << "(" << pa.first << "," << pa.second << ")"; return os; }
template<typename TK, typename TV> ostream& operator<<(ostream &os, const map<TK, TV> &mp){ os << "{"; for (auto v : mp) os << v.first << "=>" << v.second << ","; os << "}"; return os; }
template<typename TK, typename TV> ostream& operator<<(ostream &os, const unordered_map<TK, TV> &mp){ os << "{"; for (auto v : mp) os << v.first << "=>" << v.second << ","; os << "}"; return os; }
template<typename T> void ndarray(vector<T> &vec, int len) { vec.resize(len); }
template<typename T, typename... Args> void ndarray(vector<T> &vec, int len, Args... args) { vec.resize(len); for (auto &v : vec) ndarray(v, args...); }
template<typename T> void Max(T &m, const T q) { if (m < q) m = q; }
template<typename T> void Min(T &m, const T q) { if (m > q) m = q; }
template<typename T1, typename T2> pair<T1, T2> operator+(pair<T1, T2> &l, pair<T1, T2> &r) { return make_pair(l.first + r.first, l.second + r.second); }
template<typename T1, typename T2> pair<T1, T2> operator-(pair<T1, T2> &l, pair<T1, T2> &r) { return make_pair(l.first - r.first, l.second - r.second); }
#define dbg(x) cerr << #x << " = " << (x) << " (L" << __LINE__ << ") " << __FILE__ << endl;

int N;
constexpr int Nmax = 200001;
constexpr lint MOD = 1000000007;

vector<int> par;
vector<int> chi[Nmax];
vector<int> gen_count;


struct data
{
    vector<lint> a;
    data() { a = vector<lint>{1, 0, 0}; }
    data operator*(const data &r) const
    {
        data newdata;
        newdata.a[2] = (r.a[0] + r.a[1] + r.a[2]) % MOD * a[2] + (r.a[1] + r.a[2]) % MOD * a[1] + r.a[2] * a[0] % MOD;
        newdata.a[1] = r.a[0] * a[1] + r.a[1] * a[0];
        newdata.a[0] = r.a[0] * a[0];
        REP(i, 3) newdata.a[i] %= MOD;
        return newdata;
    }
};


void dfs(int now, int gen, map<int, data> &ma)
{
    gen_count[gen]++;

    data datone;
    datone.a[1] = 1;

    ma[gen] = datone;
    if (chi[now].size() == 0) return;

    dfs(chi[now][0], gen + 1, ma);
    int maxx = gen;

    FOR(i, 1, chi[now].size())
    {
        int nxt = chi[now][i];
        map<int, data> manew;
        dfs(nxt, gen + 1, manew);
        for (auto pa : manew)
        {
            Max(maxx, pa.first);
            ma[pa.first] = ma[pa.first] * pa.second;
        }
    }

    FOR(d, gen, maxx + 1)
    {
        ma[d].a[0] = (ma[d].a[0] + ma[d].a[2]) % MOD;
        ma[d].a[2] = 0;
    }
    return;
}

lint power(lint x, lint n)
{
    lint ans = 1;
    while (n>0)
    {
        if (n & 1) (ans *= x) %= MOD;
        (x *= x) %= MOD;
       n >>= 1;
    }
   return ans;
}

int main()
{
    cin >> N;
    par.resize(N + 1);
    REP(i, N)
    {
        cin >> par[i + 1];
        chi[par[i + 1]].push_back(i + 1);
    }

    gen_count.resize(N + 1);
    map<int, data> ma;
    dfs(0, 0, ma);

    lint ans = 0;
    REP(i, N + 1) (ans += power(2, N + 1 - gen_count[i]) * ma[i].a[1]) %= MOD;
    cout << ans << endl;
}


Measured memory_bytes: 100224