adventofcode2015_day25_1.js

function calcAt(row, col, generator) {
    var val;
    for (var i = 0, l = 2 * Math.max(row, col); i <= l; i++) {
        for (var j = 0; j <= i; j++) {
            val = generator(val);
            if (row == i - j && col == j) {
                return val;
            }
        }
    }
    return undefined;
}

function generator(prev) {
    if (prev === undefined) {
        return 20151125;
    }
    return (prev * 252533) % 33554393;
}

console.log(calcAt(3010 - 1, 3019 - 1, generator));