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 A033031 #15 Jul 13 2023 01:53:39
%S A033031 1,2,3,2,6,2,3,6,2,6,6,3,2,6,6,6,2,6,3,6,6,2,6,6,6,6,3,2,6,6,6,6,6,2,
%T A033031 6,6,3,6,6,6,2,6,6,6,6,6,6,2,3,6,6,6,6,6,6,2,6,6,6,6,6,3,6,6,2,6,6,6,
%U A033031 6,6,6,6,6,2,6,6,3,6,6,6,6,6,6,2,6,6,6,6,6,6,6,6,3,6,2,6,6,6,6,6,6,6
%N A033031 Squarefree kernels of 3-smooth numbers.
%H A033031 Amiram Eldar, <a href="/A033031/b033031.txt">Table of n, a(n) for n = 1..10000</a>
%F A033031 a(n) = A007947(A003586(n)).
%F A033031 a(n) = (2*0^(A022328(n)-1)) * (3*0^(A022329(n)-1)) for n>1. - _Reinhard Zumkeller_, Jul 18 2003
%F A033031 Asymptotic mean: Limit_{m->oo} (1/m) * Sum_{k=1..m} a(k) = 6. - _Amiram Eldar_, Jul 13 2023
%e A033031 A003586(17) = 64 = 2^6 -> a(17) = 2,
%e A033031 A003586(18) = 72 = 2^3 * 3^2 -> a(18) = 2*3 = 6,
%e A033031 A003586(19) = 81 = 3^4 -> a(19) = 3.
%t A033031 s = {}; m = 12; Do[n = 3^k; While[n <= 3^m, AppendTo[s, n]; n*=2], {k, 0, m}]; rad[n_] := Times @@ (First@# & /@ FactorInteger@ n); rad /@ Union[s] (* _Amiram Eldar_, Jan 29 2020 *)
%Y A033031 Cf. A003586, A007947, A022328, A022329.
%K A033031 nonn
%O A033031 1,2
%A A033031 _Reinhard Zumkeller_, Jun 21 2003