%I #18 Oct 23 2024 01:26:43
%S 1,2,3,2,3,2,127,2,3,1234567891,2,9091,3,12345678910111,2,17,113,7,2,
%T 19,3,7,2,123456789101112131415161,3,13,2,17,13,2,2,2,3,2,2,2,3,2,2,2,
%U 5,2,2,2,3,2,2,2,3,3,2,3,29,547,2,3,3,3,2,31,3,3,2,3,71,7
%N Least prime factor of A252043(n) for n > 1 with a(1) = 1.
%H Micha Fleuren, <a href="https://archive.org/details/reverse-factors">Smarandache Factors and Reverse Factors</a>.
%F a(n) = A020639(A252043(n)).
%e A252043(3) = 123 = 3 * 41, so a(3) = 3.
%o (PARI) a(n) = my(list=List(), k=1); while(#list<n, my(d=digits(k)); for (i=1, #d, listput(list, d[i])); k++;); my(m=fromdigits(Vec(list, n))); if (m==1, 1, vecmin(factor(m)[,1])); \\ _Michel Marcus_, Sep 29 2024
%Y Cf. A020639, A252043, A376274.
%K nonn,base,new
%O 1,2
%A _Jean-Marc Rebert_, Sep 27 2024