qhPc1m - Online C++0x Compiler & Debugging Tool

#include <bits/stdc++.h>
#include <ext/pb_ds/tree_policy.hpp>
#include <ext/pb_ds/assoc_container.hpp>

using namespace std;
using namespace __gnu_pbds;

typedef tree<int, null_type, less<int>, rb_tree_tag, tree_order_statistics_node_update > pbds;
// find_by_order, order_by_key

#define sp << " " <<
#define ll long long
#define ld long double
#define pb push_back
#define F first
#define S second
#define PI 3.1415926535897932384626

#define all(x) x.begin(), x.end()
#define rall(x) x.rbegin(), x.rend()
#define sortall(x) sort(all(x))
#define sortrall(x) sort(rall(x))

#define printv(v) for(auto x : v) cout << x << " "; cout << "\n"
#define printm(m) for(auto x : m) cout << x.F sp x.S << "\n"

#define make_unique(x) sortall(x); (x).resize(unique(all(x)) - (x).begin())
#define numtobin(n) bitset<32>(n).to_string()
#define bintoint(bin_str) stoi(bin_str, nullptr, 2)

struct custom_hash {
    static uint64_t splitmix64(uint64_t x) {
        x += 0x9e3779b97f4a7c15;
        x = (x ^ (x >> 30)) * 0xbf58476d1ce4e5b9;
        x = (x ^ (x >> 27)) * 0x94d049bb133111eb;
        return x ^ (x >> 31);
    }

    size_t operator()(uint64_t x) const {
        static const uint64_t FIXED_RANDOM = chrono::steady_clock::now().time_since_epoch().count();
        return splitmix64(x + FIXED_RANDOM);
    }
};

template<typename T1, typename T2>
using safe_map = unordered_map<T1, T2, custom_hash>;

template<typename T>
using safe_set = unordered_set<T, custom_hash>;

template<typename T>
void debug(T x) { cerr << x << endl; }

template<typename T, typename... Args>
void debug(T x, Args... args) { cerr << x << " "; debug(args...); }

void fastIO() {
    ios_base::sync_with_stdio(false);
    cin.tie(NULL); cout.tie(NULL);
}

void fraction() {
    cout.unsetf(ios::floatfield);
    cout.precision(10);
    cout.setf(ios::fixed,ios::floatfield);
}

void yn(bool res, bool cap = true) {
    vector<string> s = {"Yes", "YES", "No", "NO"};
    cout << ((res) ? s[0 + cap] : s[2 + cap]) << "\n";
}

void chmin(ll &x, ll y) { x = min(x, y); }
void chmax(ll &x, ll y) { x = max(x, y); }

inline ll nxt() { ll x; cin >> x; return x;}
inline ld nxtD() { ld x; cin >> x; return x;}
inline string nxtStr() { string x; cin >> x; return x;}

const int mod = 998'244'353;
const int INF = 1e9;
const ll LINF = 1e18;

const int mx = 3e5+123;
vector<vector<ll>> primes;

void primeGen(){
    primes.resize(mx);
    for(int i = 2; i < mx; i++) {
        if(!primes[i].size()) {
            for(int j = i; j < mx; j+=i)
                primes[j].pb(i);
        }
    }
}

const int N = 1e6 + 9;

int f[N], inv[N], finv[N];
void prec() {
    f[0] = 1;
    for (int i = 1; i < N; i++) f[i] = 1LL * i * f[i - 1] % mod;
    inv[1] = 1;
    for (int i = 2; i < N; i++ ) {
        inv[i] = (-(1LL * mod / i) * inv[mod % i] ) % mod;
        inv[i] = (inv[i] + mod) % mod;
    }
    finv[0] = 1;
    for (int i = 1; i < N; i++) finv[i] = 1LL * inv[i] * finv[i - 1] % mod;
}

int ncr(int n, int r) {
    if (n < r || n < 0 || r < 0) return 0;
    return 1LL * f[n] * finv[n - r] % mod * finv[r] % mod;
}

void proc(){
    primeGen();
    prec();
}

void solve() {
    int n, k; cin >> n >> k;
    safe_map<ll, ll> mp;
    for(int i = 0; i < n; i++) {
        int x; cin >> x;
        for(auto p : primes[x])
            mp[p]++;
    }


    ll ans = 0, res = 0;
    for(auto [p, c] : mp) {
        res = (ncr(n, k) - ncr(n-c, k) + mod) % mod;
        res = (res * p) % mod;
        ans = (ans + res) % mod;
    }

    cout << ans << "\n";
}

int main() {
    fastIO();
    proc();

    int tc = 1;
    tc = nxt();
    for (int t = 1; t <= tc; t++) {
        // cout << "Case " << t << ": ";
        solve();
    }
}