function zeta( s ) {
	var idx = (s-3) / 2;
	if ( idx >= ODD_POSITIVE_INTEGERS.length ) {
		return series( s );
	}
	return ODD_POSITIVE_INTEGERS[ idx ];
}
Evaluates the Riemann zeta function for an odd positive integer.

@private
@param {number} s - input value
@returns {number} function value

@example
var v = zeta( 3.0 );
// returns ~1.202