// https://stackoverflow.com/a/39575124
export default function pi(n) {
  var v = 0
  for (let i = 1; i <= n; i += 4) {
    // increment by 4
    v += 1 / i - 1 / (i + 2) // add the value of the series
  }
  return 4 * v // apply the factor at last
}
