[SDOI2017]数字表格
求$$prod_{i=1}nprod_{j=1}mf(gcd(i, j))$$,其中(f)为(fibonacci)数列
(Tle 1000, 1le n, mle {10}^6)
[egin{aligned}ans&=prod_{i=1}^nprod_{j=1}^mf(gcd(i, j)) \
&=prod_{d=1}^nf(d)^{sum_{i=1}^nsum_{j=1}^m[gcd(i,j) == d]} \
&=prod_{d=1}^nf(d)^{sum_{x=1}^{lfloorfrac{n}{d}
floor}mu(x)lfloorfrac{n}{xd}
floorlfloorfrac{m}{xd}
floor}\
&=prod_{T=1}^n(prod_{d|T}f(d)^{mu(frac{T}{d})})^{lfloorfrac{n}{T}
floorlfloorfrac{m}{T}
floor} end{aligned}
]
先暴力筛(G(T)=prod_{d|T}f(d)^{mu(frac{T}{d})})
就可以(O(sqrt{N}logN))的时间算$$prod_{T=1}nG(T){lfloorfrac{n}{T}
floorlfloorfrac{m}{T}
floor}$$
ll pow(ll x, ll k){ll res=1; while(k){if(k&1) res=res*x%p; x=x*x%p; k >>= 1;} return res;}
void init(){
miu[1]=1; f[1]=invf[1]=1; g[1]=g[0]=1;
for(int i=2; i < Maxn; i++){
if(!pr[i]) pr[++ptot]=i, miu[i]=-1;
f[i]=(f[i-1]+f[i-2])%p; invf[i]=pow(f[i], p-2); g[i]=1;
for(int j=1, x; j <= ptot && (x=pr[j]*i) < Maxn; j++){
pr[x]=1; if(i%pr[j] == 0) break; miu[x]=-miu[i];
}
}
for(int i=1; i < Maxn; i++) if(miu[i]) for(int j=i; j < Maxn; j+=i)
g[j]=g[j]*(miu[i] > 0 ? f[j/i] : invf[j/i])%p;
for(int i=2; i < Maxn; i++) g[i]=g[i-1]*g[i]%p;
}
void solve(){
init(); int T=read();
while(T--){
n=read(), m=read(); if(n > m) swap(n, m); ll ans=1;
for(ll l=1, r=0; r < n; l=r+1){
r=min(n/(n/l), m/(m/l)); ll delta=g[r]*pow(g[l-1], p-2)%p;
ans=ans*pow(delta, (n/l)*(m/l))%p;
}
printf("%lld
", ans);
}
}