function upperIncompleteGammaFract( a1, z1 ) {
	var z = z1 - a1 + 1.0;
	var a = a1;
	var k = 0;
	return next;

	/**
	* Calculate the next term of the series.
	*
	* @private
	* @returns {Array} series expansion terms
	*/
	function next() {
		k += 1;
		z += 2.0;
		return [
			k * (a - k),
			z
		];
	}
}
Creates a function to evaluate a series expansion of the upper incomplete gamma fraction.

@private
@param {number} a1 - function parameter
@param {number} z1 - function parameter
@returns {Function} series function