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 A086410 #15 Feb 05 2020 08:53:38 %S A086410 1,2,3,2,2,2,3,2,2,2,2,3,2,2,2,2,2,2,3,2,2,2,2,2,2,2,3,2,2,2,2,2,2,2, %T A086410 2,2,3,2,2,2,2,2,2,2,2,2,2,2,3,2,2,2,2,2,2,2,2,2,2,2,2,3,2,2,2,2,2,2, %U A086410 2,2,2,2,2,2,2,2,3,2,2,2,2,2,2,2,2,2,2,2,2,2,2,2,3,2,2,2,2,2,2,2,2,2 %N A086410 Smallest prime factor of 3-smooth numbers, with a(1)=1. %H A086410 Amiram Eldar, <a href="/A086410/b086410.txt">Table of n, a(n) for n = 1..10000</a> %F A086410 a(n) = A020639(A003586(n)); %F A086410 a(n) <= A086411(n) <= 3. %F A086410 a(A033845(n)) = A086411(A033845(n))-1; a(A006899(n)) = A086411(A006899(n)). - _Reinhard Zumkeller_, Sep 25 2008 %t A086410 Reap[For[n = 1, n <= 2*10^5, n++, If[EulerPhi[6*n] == 2*n, Sow[ FactorInteger[n][[1, 1]]]]]][[2, 1]] (* _Jean-François Alcover_, Sep 02 2016 *) %Y A086410 Cf. A003586, A006899, A020639, A033845, A086411. %K A086410 nonn,nice %O A086410 1,2 %A A086410 _Reinhard Zumkeller_, Jul 18 2003