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 A086411 Greatest prime factor of 3-smooth numbers. 5

%I

%S 1,2,3,2,3,2,3,3,2,3,3,3,2,3,3,3,2,3,3,3,3,2,3,3,3,3,3,2,3,3,3,3,3,2,

%T 3,3,3,3,3,3,2,3,3,3,3,3,3,2,3,3,3,3,3,3,3,2,3,3,3,3,3,3,3,3,2,3,3,3,

%U 3,3,3,3,3,2,3,3,3,3,3,3,3,3,3,2,3,3,3,3,3,3,3,3,3,3,2,3,3,3,3,3,3,3

%N Greatest prime factor of 3-smooth numbers.

%C a(n) = A006530(A003586(n)).

%C A086410(n) <= a(n) <= 3.

%C a(A033845(n)) = A086410(A033845(n))+1; a(A006899(n)) = A086410(A006899(n)). [_Reinhard Zumkeller_, Sep 25 2008]

%t Reap[Do[p = FactorInteger[n][[-1, 1]]; If[p < 5, Sow[p]], {n, 1, 2*10^5}] ][[2, 1]] (* _Jean-François Alcover_, Dec 17 2017 *)

%Y Cf. A003586, A006530, A006899, A033845, A086410.

%K nonn

%O 1,2

%A _Reinhard Zumkeller_, Jul 18 2003

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Last modified October 15 22:25 EDT 2019. Contains 328038 sequences. (Running on oeis4.)