function coefficients( n ) {
	var coefs;
	var half;
	var high;
	var low;
	var p;
	var a;
	var b;
	var m;
	var i;

	coefs = cache[ n ];
	if ( coefs === void 0 ) {
		m = n + 1;
		coefs = new Array( m );
		if ( n === 0 ) {
			coefs[ 0 ] = 2.0;
		} else {
			for ( i = 0; i < m; i++ ) {
				coefs[ i ] = 0.0;
			}
			half = n / 2;
			high = ceil( half );
			low = floor( half );
			for ( i = 0; i <= low; i++ ) {
				p = (2*i) + (n%2);
				a = 2.0 * binomcoef( high+i-1, low-i-1 );
				b = binomcoef( high+i-1, low-i );
				coefs[ p ] += a + b;
			}
		}
		// Memoize the coefficients:
		cache[ n ] = coefs;
	}
	return coefs;
}
Computes polynomial coefficients.

## Notes

-   Coefficients are computed via a (1,2)-Pascal triangle (i.e., Lucas triangle). For more details, see [Lucas polynomials][oeis-lucas-polynomials] and [Lucas triangle][oeis-lucas-triangle].

[oeis-lucas-polynomials]: https://oeis.org/wiki/Lucas_polynomials
[oeis-lucas-triangle]: https://oeis.org/wiki/Lucas_triangle

@private
@param {NonNegativeInteger} n - Lucas polynomial for which to compute coefficients
@returns {NonNegativeIntegerArray} polynomial coefficients