A080670(n)=if(n>1, my(f=factor(n), s=""); for(i=1, #f~, s=Str(s, f[i, 1], if(f[i, 2]>1, f[i, 2], ""))); eval(s), 1)

wanted = vector(10 000)
u = 1

{
	n = 1;
	while (u <= #wanted,
		v = A080670(n);
		while (v>=u,
			if (v <= #wanted && wanted[v]==0,
				wanted[v] = n
			);
			v \= 10;
		);
		while (u <= #wanted && wanted[u],
			print (u " " wanted[u]);
			u++;
		);
		n++;
	);
}

quit