#include<stdio.h>
#include<iostream>
#include<vector>
#include<algorithm>
#include<string>
#include<string.h>

#ifdef LOCAL
#define eprintf(...) fprintf(stderr, __VA_ARGS__)
#else
#define NDEBUG
#define eprintf(...) do {} while (0)
#endif
#include<cassert>

using namespace std;

typedef long long LL;
typedef vector<int> VI;

#define REP(i,n) for(int i=0, i##_len=(n); i<i##_len; ++i)
#define EACH(i,c) for(__typeof((c).begin()) i=(c).begin(),i##_end=(c).end();i!=i##_end;++i)

template<class T> inline void amin(T &x, const T &y) { if (y<x) x=y; }
template<class T> inline void amax(T &x, const T &y) { if (x<y) x=y; }
template<class Iter> void rprintf(const char *fmt, Iter begin, Iter end) {
    for (bool sp=0; begin!=end; ++begin) { if (sp) putchar(' '); else sp = true; printf(fmt, *begin); }
    putchar('\n');
}
template<unsigned MOD_> struct ModInt {
    static const unsigned MOD = MOD_;
    unsigned x;
    void undef() { x = (unsigned)-1; }
    bool isnan() const { return x == (unsigned)-1; }
    inline int geti() const { return (int)x; }
    ModInt() { x = 0; }
    ModInt(const ModInt &y) { x = y.x; }
    ModInt(int y) { if (y<0 || (int)MOD<=y) y %= (int)MOD; if (y<0) y += MOD; x=y; }
    ModInt(unsigned y) { if (MOD<=y) x = y % MOD; else x = y; }
    ModInt(long long y) { if (y<0 || MOD<=y) y %= MOD; if (y<0) y += MOD; x=y; }
    ModInt(unsigned long long y) { if (MOD<=y) x = y % MOD; else x = y; }
    ModInt &operator+=(const ModInt y) { if ((x += y.x) >= MOD) x -= MOD; return *this; }
    ModInt &operator-=(const ModInt y) { if ((x -= y.x) & (1u<<31)) x += MOD; return *this; }
    ModInt &operator*=(const ModInt y) { x = (unsigned long long)x * y.x % MOD; return *this; }
    ModInt &operator/=(const ModInt y) { x = (unsigned long long)x * y.inv().x % MOD; return *this; }
    ModInt operator-() const { return (x ? MOD-x: 0); }

    ModInt inv() const { return pow(MOD-2); }
    ModInt pow(long long y) const {
	ModInt b = *this, r = 1;
	if (y < 0) { b = b.inv(); y = -y; }
	for (; y; y>>=1) {
	    if (y&1) r *= b;
	    b *= b;
	}
	return r;
    }

    ModInt extgcd() const {
	unsigned a = MOD, b = x; int u = 0, v = 1;
	while (b) {
	    int t = a / b;
	    a -= t * b; swap(a, b);
	    u -= t * v; swap(u, v);
	}
	if (u < 0) u += MOD;
	return ModInt(u);
    }

    friend ModInt operator+(ModInt x, const ModInt y) { return x += y; }
    friend ModInt operator-(ModInt x, const ModInt y) { return x -= y; }
    friend ModInt operator*(ModInt x, const ModInt y) { return x *= y; }
    friend ModInt operator/(ModInt x, const ModInt y) { return x *= y.inv(); }
    friend bool operator<(const ModInt x, const ModInt y) { return x.x < y.x; }
    friend bool operator==(const ModInt x, const ModInt y) { return x.x == y.x; }
    friend bool operator!=(const ModInt x, const ModInt y) { return x.x != y.x; }
};

const LL MOD = 1000000007;

typedef ModInt<MOD> Mint;

int N;
VI G[2011];
int sz[2011];
Mint dp[2011][2011][3];
Mint buf[2][2011][3];
Mint (*cur)[3] = buf[0];
Mint (*nxt)[3] = buf[1];

void MAIN() {
    scanf("%d", &N);
    REP (i, N-1) {
	int p;
	scanf("%d", &p);
	p--;
	G[p].push_back(i+1);
    }
    
    for (int v=N; v--;) {
	sz[v] = 1;
	memset(cur, 0, sizeof buf[0]);
	cur[1][0] = 1;
	EACH (e, G[v]) {
	    memset(nxt, 0, sizeof buf[0]);
	    for (int a=1; a<=sz[v]; a++) {
		for (int b=0; b<3; b++) {
		    for (int c=1; c<=sz[*e]; c++) {
			for (int d=0; d<3; d++) {
			    Mint tmp = cur[a][b] * dp[*e][c][d];
			    nxt[a+c][b] += tmp + (d? tmp: 0);
			    if (b < 2 && d < 2) nxt[a+c-1][b+1] += tmp;
			}
		    }
		}
	    }

	    sz[v] += sz[*e];
	    swap(cur, nxt);
	}

	REP (a, sz[v] + 1) REP (b, 3) dp[v][a][b] = cur[a][b];
    }

    Mint ans = 0;
    Mint f = 1;
    REP (a, N+1) {
	REP (b, 3) {
	    Mint tmp = dp[0][a][b];
	    if (b) tmp += tmp;
	    tmp *= f;
	    if ((N-a)%2) ans -= tmp;
	    else ans += tmp;
	}
	f *= a+1;
    }

    printf("%d\n", ans.geti());
}

int main() {
    int TC = 1;
//    scanf("%d", &TC);
    REP (tc, TC) MAIN();
    return 0;
}

