T1 经过一波大力推式子,发现答案是 \(\frac{n^{2}-1}{9}\) . 式子回头再补,可能会 Code #include<cstdio> #define re register #define int long long namespace OMA { int t,n; const int p = 998244353; inline int read() { int s=0,w=1; char ch=getchar(); while(ch<'0'||ch>'9'){…