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Greatest prime factor of 7-smooth numbers.
2

%I #15 Feb 21 2020 05:23:50

%S 1,2,3,2,5,3,7,2,3,5,3,7,5,2,3,5,7,3,5,3,7,5,2,7,3,5,7,5,3,7,5,3,7,5,

%T 7,2,7,3,5,5,3,7,5,3,7,5,7,3,7,5,5,7,2,5,7,3,7,5,5,3,7,7,5,7,3,7,5,7,

%U 3,7,5,5,3,7,5,7,2,5,7,3,7,5,7,5,3,7,7,7,5,5,7,3,7,5,5,7,3,7,7,5

%N Greatest prime factor of 7-smooth numbers.

%H Amiram Eldar, <a href="/A086287/b086287.txt">Table of n, a(n) for n = 1..10000</a>

%F a(n) = A006530(A002473(n)).

%F A086286(n) <= a(n) <= 7.

%t Reap[Do[p = FactorInteger[n][[-1, 1]]; If[p < 11, Sow[p]], {n, 1, 500}] ][[2, 1]] (* _Jean-François Alcover_, Dec 17 2017 *)

%Y Cf. A002473, A006530, A086286.

%K nonn

%O 1,2

%A _Reinhard Zumkeller_, Jul 15 2003