description: Mr. Chanek has an array a of n integers. The prettiness value of a is denoted as:
  
  $$$∑_{i=1}^{n} {∑_{j=1}^{n} {\gcd(a_i, a_j) ⋅ \gcd(i, j)}}$$$
  
  where \gcd(x, y) denotes the greatest common divisor (GCD) of integers x and y.
  
  In other words, the prettiness value of an array a is the total sum of \gcd(a_i, a_j) ⋅ \gcd(i, j) for all pairs (i, j).
  
  Help Mr. Chanek find the prettiness value of a, and output the result modulo 10^9 + 7!
  
  Input
  
  The first line contains an integer n (2 ≤ n ≤ 10^5).
  
  The second line contains n integers a_1, a_2, …, a_n (1 ≤ a_i ≤ 10^5).
  
  Output
  
  Output an integer denoting the prettiness value of a modulo 10^9 + 7.
  
  Example
  
  Input
  
  
  5
  3 6 2 1 4
  
  
  Output
  
  
  77
solution: #include <bits/stdc++.h>
  using namespace std;
  template <typename T>
  T inverse(T a, T m) {
    T u = 0, v = 1;
    while (a != 0) {
      T t = m / a;
      m -= t * a;
      swap(a, m);
      u -= t * v;
      swap(u, v);
    }
    assert(m == 1);
    return u;
  }
  template <typename T>
  class Modular {
   public:
    using Type = typename decay<decltype(T::value)>::type;
    constexpr Modular() : value() {}
    template <typename U>
    Modular(const U& x) {
      value = normalize(x);
    }
    template <typename U>
    static Type normalize(const U& x) {
      Type v;
      if (-mod() <= x && x < mod())
        v = static_cast<Type>(x);
      else
        v = static_cast<Type>(x % mod());
      if (v < 0) v += mod();
      return v;
    }
    const Type& operator()() const { return value; }
    template <typename U>
    explicit operator U() const {
      return static_cast<U>(value);
    }
    constexpr static Type mod() { return T::value; }
    Modular& operator+=(const Modular& other) {
      if ((value += other.value) >= mod()) value -= mod();
      return *this;
    }
    Modular& operator-=(const Modular& other) {
      if ((value -= other.value) < 0) value += mod();
      return *this;
    }
    template <typename U>
    Modular& operator+=(const U& other) {
      return *this += Modular(other);
    }
    template <typename U>
    Modular& operator-=(const U& other) {
      return *this -= Modular(other);
    }
    Modular& operator++() { return *this += 1; }
    Modular& operator--() { return *this -= 1; }
    Modular operator++(int) {
      Modular result(*this);
      *this += 1;
      return result;
    }
    Modular operator--(int) {
      Modular result(*this);
      *this -= 1;
      return result;
    }
    Modular operator-() const { return Modular(-value); }
    template <typename U = T>
    typename enable_if<is_same<typename Modular<U>::Type, int>::value,
                       Modular>::type&
    operator*=(const Modular& rhs) {
      value = normalize(static_cast<int64_t>(value) *
                        static_cast<int64_t>(rhs.value));
      return *this;
    }
    template <typename U = T>
    typename enable_if<is_same<typename Modular<U>::Type, long long>::value,
                       Modular>::type&
    operator*=(const Modular& rhs) {
      long long q = static_cast<long long>(static_cast<long double>(value) *
                                           rhs.value / mod());
      value = normalize(value * rhs.value - q * mod());
      return *this;
    }
    template <typename U = T>
    typename enable_if<!is_integral<typename Modular<U>::Type>::value,
                       Modular>::type&
    operator*=(const Modular& rhs) {
      value = normalize(value * rhs.value);
      return *this;
    }
    Modular& operator/=(const Modular& other) {
      return *this *= Modular(inverse(other.value, mod()));
    }
    friend const Type& abs(const Modular& x) { return x.value; }
    template <typename U>
    friend bool operator==(const Modular<U>& lhs, const Modular<U>& rhs);
    template <typename U>
    friend bool operator<(const Modular<U>& lhs, const Modular<U>& rhs);
    template <typename V, typename U>
    friend V& operator>>(V& stream, Modular<U>& number);
  
   private:
    Type value;
  };
  template <typename T>
  bool operator==(const Modular<T>& lhs, const Modular<T>& rhs) {
    return lhs.value == rhs.value;
  }
  template <typename T, typename U>
  bool operator==(const Modular<T>& lhs, U rhs) {
    return lhs == Modular<T>(rhs);
  }
  template <typename T, typename U>
  bool operator==(U lhs, const Modular<T>& rhs) {
    return Modular<T>(lhs) == rhs;
  }
  template <typename T>
  bool operator!=(const Modular<T>& lhs, const Modular<T>& rhs) {
    return !(lhs == rhs);
  }
  template <typename T, typename U>
  bool operator!=(const Modular<T>& lhs, U rhs) {
    return !(lhs == rhs);
  }
  template <typename T, typename U>
  bool operator!=(U lhs, const Modular<T>& rhs) {
    return !(lhs == rhs);
  }
  template <typename T>
  bool operator<(const Modular<T>& lhs, const Modular<T>& rhs) {
    return lhs.value < rhs.value;
  }
  template <typename T>
  Modular<T> operator+(const Modular<T>& lhs, const Modular<T>& rhs) {
    return Modular<T>(lhs) += rhs;
  }
  template <typename T, typename U>
  Modular<T> operator+(const Modular<T>& lhs, U rhs) {
    return Modular<T>(lhs) += rhs;
  }
  template <typename T, typename U>
  Modular<T> operator+(U lhs, const Modular<T>& rhs) {
    return Modular<T>(lhs) += rhs;
  }
  template <typename T>
  Modular<T> operator-(const Modular<T>& lhs, const Modular<T>& rhs) {
    return Modular<T>(lhs) -= rhs;
  }
  template <typename T, typename U>
  Modular<T> operator-(const Modular<T>& lhs, U rhs) {
    return Modular<T>(lhs) -= rhs;
  }
  template <typename T, typename U>
  Modular<T> operator-(U lhs, const Modular<T>& rhs) {
    return Modular<T>(lhs) -= rhs;
  }
  template <typename T>
  Modular<T> operator*(const Modular<T>& lhs, const Modular<T>& rhs) {
    return Modular<T>(lhs) *= rhs;
  }
  template <typename T, typename U>
  Modular<T> operator*(const Modular<T>& lhs, U rhs) {
    return Modular<T>(lhs) *= rhs;
  }
  template <typename T, typename U>
  Modular<T> operator*(U lhs, const Modular<T>& rhs) {
    return Modular<T>(lhs) *= rhs;
  }
  template <typename T>
  Modular<T> operator/(const Modular<T>& lhs, const Modular<T>& rhs) {
    return Modular<T>(lhs) /= rhs;
  }
  template <typename T, typename U>
  Modular<T> operator/(const Modular<T>& lhs, U rhs) {
    return Modular<T>(lhs) /= rhs;
  }
  template <typename T, typename U>
  Modular<T> operator/(U lhs, const Modular<T>& rhs) {
    return Modular<T>(lhs) /= rhs;
  }
  template <typename T, typename U>
  Modular<T> power(const Modular<T>& a, const U& b) {
    assert(b >= 0);
    Modular<T> x = a, res = 1;
    U p = b;
    while (p > 0) {
      if (p & 1) res *= x;
      x *= x;
      p >>= 1;
    }
    return res;
  }
  template <typename T>
  bool IsZero(const Modular<T>& number) {
    return number() == 0;
  }
  template <typename T>
  string to_string(const Modular<T>& number) {
    return to_string(number());
  }
  template <typename U, typename T>
  U& operator<<(U& stream, const Modular<T>& number) {
    return stream << number();
  }
  template <typename U, typename T>
  U& operator>>(U& stream, Modular<T>& number) {
    typename common_type<typename Modular<T>::Type, long long>::type x;
    stream >> x;
    number.value = Modular<T>::normalize(x);
    return stream;
  }
  constexpr int md = (int)1e9 + 7;
  using Mint = Modular<std::integral_constant<decay<decltype(md)>::type, md>>;
  vector<Mint> fact(1, 1);
  vector<Mint> inv_fact(1, 1);
  Mint C(int n, int k) {
    if (k < 0 || k > n) {
      return 0;
    }
    while ((int)fact.size() < n + 1) {
      fact.push_back(fact.back() * (int)fact.size());
      inv_fact.push_back(1 / fact.back());
    }
    return fact[n] * inv_fact[k] * inv_fact[n - k];
  }
  int main() {
    ios::sync_with_stdio(false);
    cin.tie(0);
    int n;
    cin >> n;
    vector<int> a(n + 1);
    for (int i = 1; i <= n; i++) cin >> a[i];
    vector<Mint> dp(n + 1);
    const int N = (int)1e5;
    vector<vector<int>> u(N + 1);
    for (int i = 1; i <= N; i++) {
      for (int j = i; j <= N; j += i) u[j].push_back(i);
    }
    vector<int> cnt(N + 1);
    vector<Mint> val(N + 1);
    auto solve = [&](vector<int>& a) {
      Mint ans = 0;
      vector<int> now;
      for (auto& x : a) {
        for (auto& y : u[x]) {
          if (!cnt[y]++) now.push_back(y);
        }
      }
      sort(now.rbegin(), now.rend());
      for (auto& x : now) {
        val[x] += Mint(cnt[x]) * cnt[x];
        for (auto& y : u[x]) {
          if (x == y) continue;
          val[y] -= val[x];
        }
        ans += val[x] * x;
      }
      for (auto& x : now) {
        cnt[x] = 0;
        val[x] = 0;
      }
      return ans;
    };
    for (int i = 1; i <= n; i++) {
      vector<int> now;
      for (int j = i; j <= n; j += i) {
        now.push_back(a[j]);
      }
      dp[i] = solve(now);
    }
    Mint ans = 0;
    for (int i = n; i >= 1; i--) {
      for (int j = i + i; j <= n; j += i) {
        dp[i] -= dp[j];
      }
      ans += dp[i] * i;
    }
    cout << ans;
  }
  