#include <bits/stdc++.h>
using namespace std;
void read(int &x) {
  int v = 0, f = 1;
  char c = getchar();
  while (!isdigit(c) && c != '-') c = getchar();
  if (c == '-')
    f = -1;
  else
    v = v * 10 + c - '0';
  while (isdigit(c = getchar())) v = v * 10 + c - '0';
  x = v * f;
}
void read(long long &x) {
  long long v = 0ll, f = 1ll;
  char c = getchar();
  while (!isdigit(c) && c != '-') c = getchar();
  if (c == '-')
    f = -1;
  else
    v = v * 10 + c - '0';
  while (isdigit(c = getchar())) v = v * 10 + c - '0';
  x = v * f;
}
void readc(char &x) {
  char c;
  while ((c = getchar()) == ' ')
    ;
  x = c;
}
void writes(string s) { puts(s.c_str()); }
void writeln() { writes(""); }
void writei(int x) {
  if (x < 0) {
    putchar('-');
    x = abs(x);
  }
  if (!x) putchar('0');
  char a[25];
  int top = 0;
  while (x) {
    a[++top] = (x % 10) + '0';
    x /= 10;
  }
  while (top) {
    putchar(a[top]);
    top--;
  }
}
void writell(long long x) {
  if (x < 0) {
    putchar('-');
    x = abs(x);
  }
  if (!x) putchar('0');
  char a[25];
  int top = 0;
  while (x) {
    a[++top] = (x % 10) + '0';
    x /= 10;
  }
  while (top) {
    putchar(a[top]);
    top--;
  }
}
inline long long inc(int &x) { return ++x; }
inline long long inc(long long &x) { return ++x; }
inline long long inc(int &x, long long y) { return x += y; }
inline long long inc(long long &x, long long y) { return x += y; }
inline double inc(double &x, double y) { return x += y; }
inline long long dec(int &x) { return --x; }
inline long long dec(long long &x) { return --x; }
inline long long dec(int &x, long long y) { return x -= y; }
inline long long dec(long long &x, long long y) { return x -= y; }
inline double dec(double &x, double y) { return x -= y; }
inline long long mul(int &x) { return x = ((long long)x) * x; }
inline long long mul(long long &x) { return x = x * x; }
inline long long mul(int &x, long long y) { return x *= y; }
inline long long mul(long long &x, long long y) { return x *= y; }
inline double mul(double &x, double y) { return x *= y; }
inline long long divi(const int &x) {
  long long ans, l, r, mid;
  ans = 0;
  l = 0;
  r = 0x3fffffff;
  while (l < r) {
    mid = (l + r) / 2;
    if (mid * mid <= x) {
      ans = mid;
      l = mid + 1;
    } else
      r = mid;
  }
  return ans;
}
inline long long divi(const long long &x) {
  long long ans, l, r, mid;
  ans = 0;
  l = 0;
  r = 0x3fffffff;
  while (l < r) {
    mid = (l + r) / 2;
    if (mid * mid <= x) {
      ans = mid;
      l = mid + 1;
    } else
      r = mid;
  }
  return ans;
}
inline long long divi(int &x, long long y) { return x /= y; }
inline long long divi(long long &x, long long y) { return x /= y; }
inline double divi(double &x, double y) { return x /= y; }
inline long long mod(int &x, long long y) { return x %= y; }
inline long long mod(long long &x, long long y) { return x %= y; }
int t, n, m, i, j, a[500005];
string st;
char ss[500005];
vector<int> ans;
bool check(int x) {
  int i;
  if ((1) <= ((x)))
    for (((i)) = (1); ((i)) <= ((x)); ((i))++) {
      int t = 0, j = i + x;
      char now = st[i];
      while (j <= n) {
        if (now != '?' && st[j] != '?' && now != st[j]) return 0;
        if (now == '?') now = st[j];
        j += x;
      }
    }
  return 1;
}
int main() {
  scanf("%d", &t);
  while (t--) {
    scanf("%d", &n);
    scanf(" %s", ss);
    st = ss;
    st = " " + st;
    if ((1) <= ((n)))
      for (((i)) = (1); ((i)) <= ((n)); ((i))++) a[i] = 0;
    ans.clear();
    int cnt = 0;
    if (check(1)) {
      printf("%d\n", n);
      if ((1) <= ((n)))
        for (((i)) = (1); ((i)) <= ((n)); ((i))++) printf("%d ", i);
      puts("");
      continue;
    }
    for (i = 2; i <= n; i++) {
      if (!a[i]) {
        a[i] = check(i);
      } else if (a[i] == 1)
        for (j = 2; i * j <= n; j++) a[i * j] = a[i];
    }
    if ((1) <= ((n)))
      for (((i)) = (1); ((i)) <= ((n)); ((i))++)
        if (a[i]) ans.push_back(i);
    printf("%d\n", ans.size());
    for (__typeof((ans).begin()) it = (ans).begin(); it != (ans).end(); it++)
      printf("%d ", *it);
    puts("");
  }
  return 0;
}
