aboveTheMainDiagonal.js

//col      0  1  2  3
//row 0 -  1  2  4  8
//row 1 -  2  4  8 16
//row 2 -  4  8 16 32
//row 3 -  8 16 32 64

let matN = +gets();
let rows = matN;
let cols = matN;
let matrix = [];
let sum = 0;

for(let row = 0; row < rows; row++){
    matrix[row] = [];
    for(let col = 0; col < cols; col++){
        matrix[row][col] = 2**(row + col)
    }
}
console.log(matrix);
for(let firstCount = matN - 1; firstCount > 0; firstCount--){
    for(let row = firstCount; row < matN; row++){
        for(let col = 0; col < matN; col++){
        if((row-col) === firstCount){
            sum = sum + (matrix[row][col]);
        }
        }
    }
}
console.log(sum);