function next() {
		var denom;
		var aN;
		var bN;

		aN = (a + m - 1) * (a + b + m - 1) * m * (b - m) * x * x;
		denom = a + ( 2.0*m ) - 1.0;
		aN /= denom * denom;
		bN = m;
		bN += (m * (b - m) * x) / ( a + ( 2.0*m ) - 1.0 );
		bN += ( (a+m) * ( (a*y) - (b*x) + 1.0 + ( m*(2.0-x) ) ) ) / ( a + (2.0*m) + 1.0 ); // eslint-disable-line max-len
		m += 1;
		return [ aN, bN ];
	}
Calculate the numerator and denominator of the next term of the series.

@private
@returns {Array} series expansion terms