function finiteGammaQ( a, x ) {
	var term;
	var sum;
	var e;
	var n;

	e = exp( -x );
	sum = e;
	if ( sum !== 0.0 ) {
		term = sum;
		for ( n = 1; n < a; ++n ) {
			term /= n;
			term *= x;
			sum += term;
		}
	}
	return sum;
}
Calculates normalized Q when a is an integer.

@private
@param {integer} a - function parameter
@param {number} x - function parameter
@returns {number} upper gamma fraction