You are given an array of integers
a1, a2, …, ana_1, \ a_2, \ \dots , \ a_na1, a2, …, an.
Define
bi,j(1≤i<j≤n)=a1, a2, … , ai−1, aj, aj−1, … , ai+1, ai, aj+1,b_{i,j}(1 \le i <j \le n )= a_1, \ a_2, \ \dots \ , \ a_{i-1}, \ a_j, \ a_{j-1}, \ \dots \ , \ a_{i+1}, \ a_i, \ a_{j+1},bi,j(1≤i<j≤n)=a1, a2, … , ai−1, aj, aj−1, … , ai+1, ai, aj+1, … , an\dots \ , \ a_n… , an. Which means you choose two indexes
iii and
jjj, then reverse
ai, ai+1, … aj−1, aja_i,\ a_{i+1}, \ \dots \, \ a_{j-1}, \ a_jai, ai+1, … aj−1, aj.
You should calculate for k=2k=2k=2 to 2×n2\times n2×n, (∑i=1n∑j=i+1n∑1≤x,y≤n, x+y=k(bi,j)x×(bi,j)y)(\sum_{i=1}^{n} \sum_{j=i+1}^{n} \sum_{1 \le x,y \le n, \ x+y=k} (b_{i,j})_x \times (b_{i,j})_{y})(∑i=1n∑j=i+1n∑1≤x,y≤n, x+y=k(bi,j)x×(bi,j)y) modulo 998244353998244353998244353.