private function fibanocci($n, $a = null, $b = null)
	{
		// use the initial delay if no value passed in
		$a = ($a !== null) ? $a : $this->initialDelay;
		$b = ($b !== null) ? $b : $this->initialDelay;

		if ($n) {
			return $this->fibanocci($n - 1, $b, $a + $b);
		} else {
			return $a;
		}
	}