function mgf( t, k ) {
	if (
		isnan( t ) ||
		isnan( k ) ||
		k < 0.0 ||
		t >= 0.5
	) {
		return NaN;
	}
	return pow( 1-(2*t), -k/2 );
}
Evaluates the moment-generating function (MGF) for a chi-squared distribution with degrees of freedom `k` at a value `t`.

@param {number} t - input value
@param {NonNegativeNumber} k - degrees of freedom
@returns {number} evaluated MGF

@example
var y = mgf( 0.4, 2 );
// returns ~5.0

@example
var y = mgf( -1.0, 5.0 );
// returns ~0.0642

@example
var y = mgf( 0.0, 10.0 );
// returns 1.0