big = 1 000 000
s = 0
S = Set([])
unseen = 1
seen(v) = if (v < big, bit test(s, v), set search(S, v))
see(v) = if (v < big, s = bit or(s, 2^v), S = set union(S, Set([v]))); while (seen(unseen), unseen++)

base = 3
other(p) = {
	see(p);
	my (d=Vecrev(digits(p, base)));

	\\ alter leftmost digit (no a leading zero)
	forstep (x=#d-1, 0, -1,
		for (t=0, base-1,
			my (m=p+(t-d[x+1])*base^x);
			if (!seen(m),
				return (m);
			);
		);
	);

	\\ alter rightmost leading zero
	for (x=#d, oo,
		for (t=0, base-1,
			my (m=p+t*base^x);
			if (!seen(m),
				return (m);
			);
		);
	);
}

v=0; for (n=0, base^logint(10 000, base)-1, print (n " " v); v=other(v))

quit