JAVASCRIPT

first n even numbers sum javascript

// return the sum of the first n even numbers recursively. Assume n > 0

function firstEvenNumbersSum(n) {
    if (n === 0) {
        return 0;
    }
    let num = (n * 2);
    let sum = num + firstEvenNumbersSum(n-1)
    return sum;
}

the sum of all first n natural numbers js

S(n) = n * (n + 1) / 2