function upperIncompleteGammaFract( a, z ) {
	var k = 0;
	z = z - a + 1.0;
	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} a - function parameter
@param {number} z - function parameter
@returns {Function} series function