AprilArcus

  function * makeSequence() {
    let i = 1;
    while (true) yield i++;
  }

  const ints = makeSequence();

  function sumTo(cutoff) {
    const ints = makeSequence();
    let sum = 0;
    for (let i = 0; i < cutoff; i++) {
      sum += ints.next().value;
    }
    return sum;
  }