base = 4

nb(n,d) = my (k=0); while (n, if (n%base==d, k++); n\=base); k

f(n) = 1 + nb(n,1)
g(n) = 1 + nb(n,2)

gg = []
u = 0
other(n) = {
	my (i=f(n));
	while (#gg < i || #gg[i]==0,
		my (j=g(u));
		while (#gg < j,
			gg = concat(gg, [[]]);
		);
		gg[j] = concat(gg[j], u);
		u++;
	);
	my (v=gg[i][1]);
	gg[i] = gg[i][2..-1];
	return (v);
}

for (n=0, 4^6-1, print (n " " v=other(n)))

quit