bigInt.js

// Let's define two functions:

// S(N) — sum of all positive numbers not more than N
// S(N) = 1 + 2 + 3 + ... + N

// Z(N) — sum of all S(i), where 1 <= i <= N
// Z(N) = S(1) + S(2) + S(3) + ... + S(N)
// You will be given an integer N as input; your task is to return the value of S(Z(N)).

// For example, let N = 3:

// Z(3n) = 1n + 3n + 6n = 10n
// S(Z(3n)) = S(10n) = 55n
// The input range is 1 <= N <= 10^9 and there are 80 ( 40 in LC ) test cases, of which most are random.

// This is my first kata and I hope you'll enjoy it :).
// Best of luck!

//times out for huge inputs. needs a solution without a loop

function sumOfSums(element) {
    let sum = 0n
    for (let i = 1n; i <= element; i++) {
      sum = sum + ((i*(i+1n))/2n)
    }
    return ((sum*(sum+1n))/2n)
  }