#include namespace { #pragma GCC diagnostic ignored "-Wunused-function" #include #pragma GCC diagnostic warning "-Wunused-function" using namespace std; using namespace atcoder; #define rep(i,n) for(int i = 0; i < (int)(n); i++) #define rrep(i,n) for(int i = (int)(n) - 1; i >= 0; i--) #define all(x) begin(x), end(x) #define rall(x) rbegin(x), rend(x) template bool chmax(T& a, const T& b) { if (a < b) { a = b; return true; } else return false; } template bool chmin(T& a, const T& b) { if (b < a) { a = b; return true; } else return false; } using ll = long long; using P = pair; using VI = vector; using VVI = vector; using VL = vector; using VVL = vector; using mint = modint998244353; pair, vector> primes_lpf(const int n) { vector primes; primes.reserve(n / 10); vector lpf(n + 1); for (int i = 2; i <= n; i += 2) lpf[i] = 2; for (int i = 3; i <= n; i += 6) lpf[i] = 3; if (2 <= n) primes.push_back(2); if (3 <= n) primes.push_back(3); // 5 * x <= n, x <= floor(n / 5) const int n5 = n / 5; int x = 5; char add_next = 2; for (; x <= n5; x += add_next, add_next ^= 0x2 ^ 4) { int px = lpf[x]; if (px == 0) { lpf[x] = px = x; primes.push_back(x); } for (int i = 2;; ++i) { int q = primes[i]; int y = q * x; if (y > n) break; lpf[y] = q; if (q == px) break; } } for (; x <= n; x += add_next, add_next ^= 0x2 ^ 4) { if (lpf[x] == 0) { lpf[x] = x; primes.push_back(x); } } return {move(primes), move(lpf)}; } constexpr int PSIZE = 1000000; auto [primes, lpf] = primes_lpf(PSIZE); vector& divisors_lv(int x) { int ps[10], cs[10]; int sz = 0; while (x != 1) { int p = lpf[x], c = 0; do {x /= p; c++;} while (x % p == 0); ps[sz] = p; cs[sz] = c; sz++; } static vector res; res.clear(); res.emplace_back(1); for (int i = 0; i < sz; i++) { int p = ps[i], ptr = 0; for (int t = cs[i] * res.size(); t > 0; t--) res.emplace_back(res[ptr++] * p); } return res; } constexpr int FACT_SIZE = 1000000; mint Fact[FACT_SIZE + 1]; mint iFact[FACT_SIZE + 1]; const auto fact_init = [] { Fact[0] = mint::raw(1); for(int i = 1; i <= FACT_SIZE; ++i) { Fact[i] = Fact[i-1] * i; } iFact[FACT_SIZE] = Fact[FACT_SIZE].inv(); for(int i = FACT_SIZE; i; --i) { iFact[i-1] = iFact[i] * i; } return false; }(); mint comb(int n, int k) { if (k == 0) return mint::raw(1); assert(n >= 0 && k >= 0); if (k > n) return mint::raw(0); return Fact[n] * iFact[n - k] * iFact[k]; } mint icomb(int n, int k) { return iFact[n] * Fact[n - k] * Fact[k]; } mint fact(int n) {return Fact[n];} mint perm(int n, int k) { assert(0 <= n); return Fact[n] * iFact[n - k]; } } int main() { ios::sync_with_stdio(false); cin.tie(0); int tt; cin >> tt; while (tt--) { int n, a; cin >> n >> a; n--; mint ans; for (int d : divisors_lv(a)) { int c = a / d; // [x^c](x+x^-1)^n // a-b = c // a+b = n if (c % 2 != n % 2) continue; int a = (c + n) / 2; int b = (n - c) / 2; if (b < 0) continue; ans += comb(a+b, b); if (b) ans -= comb(a+b, b-1); } cout << ans.val() << '\n'; } }