cat(x,y) = x*10^#digits(y)+y

explore(v, rem, t) = {
	if (#rem==0,
		if (v<best[#best],
			my (d=digits(v));
			for (k=1, #d,
				best[k] = fromdigits(d[1..k]);
			);
		),

		for (r=1, #rem,
			if (t==0 || isprime(t+rem[r]),
				my (vv=cat(v, rem[r]));
				if (vv<=best[#digits(vv)],
					explore(vv, concat(rem[1..r-1], rem[r+1..#rem]), rem[r]);
				);
			);
		);
	);
}

opt(x,y) = {
	my (d=digits(x)[1]-digits(y)[1]);
	if (d, return (d), return (x-y));
}

a(n) = {
	my (w=sum(k=1, n, #digits(k)));
	best = vector(w, k, oo);
	explore(0, vecsort([1..n], opt), 0);
	best[w];
}

for (n=1, 100, print (n " " a(n)))

quit