This is a front-end for the Online Encyclopedia of Integer Sequences, made by Christian Perfect. The idea is to provide OEIS entries in non-ancient HTML, and then to think about how they're presented visually. The source code is on GitHub.
%I A122443 #12 Mar 04 2017 13:50:09
%S A122443 1,2,2,3,2,2,3,2,3,2,5,2,3,2,5,2,2,3,2,7,3,5,3,2,2,2,5,3,2,7,3,2,5,2,
%T A122443 3,7,3,2,5,2,2,3,5,2,7,11,2,3,3,7,2,3,2,11,5,2,5,2,3,7,2,13,3,2,3,5,
%U A122443 11,2,2,3,2,7,5,2,11,3,2,5,2,7,2,3,13,3,2,5,3,13
%N A122443 Least prime factor of powers of semiprimes.
%H A122443 Michael De Vlieger, <a href="/A122443/b122443.txt">Table of n, a(n) for n = 1..10000</a>
%F A122443 a(n) = A020639(A085155(n)) = least prime factor of A085155 powers of semiprimes.
%t A122443 FactorInteger[#][[1, 1]] & /@ Select[Range@ 250, Function[n, Or[n == 1, And[Length@ # == 1, EvenQ@ First@ #], And[Length@ # == 2, SameQ @@ #]] &[FactorInteger[n][[All, -1]]]]] (* _Michael De Vlieger_, Mar 04 2017 *)
%o A122443 (PARI) is(n)=my(f=factor(n)[, 2]); #f==0 || (#f==2 && f[1]==f[2]) || (#f==1 && f[1]%2==0);
%o A122443 spf(n) = if (n==1, 1, factor(n)[1,1]);
%o A122443 lista(nn) = {for (n=1, nn, if (is(n), print1(spf(n), ", ")););} \\ _Michel Marcus_, Mar 04 2017
%Y A122443 Cf. A000040, A001358, A020639, A076396, A085155.
%Y A122443 Cf. A122444 (greatest prime factor of powers of semiprimes).
%Y A122443 Cf. A076396 (smallest prime factor of n-th perfect power).
%K A122443 easy,nonn
%O A122443 1,2
%A A122443 _Jonathan Vos Post_, Sep 06 2006
%E A122443 More terms from _Michel Marcus_, Mar 04 2017