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A112763 Smallest prime factor of the n-th 5-smooth number.

%I A112763 #13 Sep 08 2022 08:45:23
%S A112763 1,2,3,2,5,2,2,3,2,2,3,2,2,2,2,5,3,2,2,2,2,3,2,2,2,2,2,2,3,2,3,2,2,2,
%T A112763 2,2,5,2,3,2,2,2,2,2,2,2,2,3,2,3,2,2,2,2,2,2,2,2,3,2,2,3,2,2,2,2,2,2,
%U A112763 2,2,2,5,2,2,3,2,3,2,2,2,2,2,2,2,2,2,2,2,3,2,2,3,2,2,2,2,2,2,2,2,2,2,2,2,3
%N A112763 Smallest prime factor of the n-th 5-smooth number.
%H A112763 Amiram Eldar, <a href="/A112763/b112763.txt">Table of n, a(n) for n = 1..10000</a>
%F A112763 a(n) = A020639(A051037(n));
%F A112763 a(n) <= A112764(n) <= 5.
%F A112763 a(A188427(n)) = 5 for n > 1. - _David A. Corneth_, Feb 07 2020
%t A112763 FactorInteger[#][[1, 1]] & /@ Select[Range[3000], Last @ Map[First, FactorInteger[#]] <= 5 &] (* _Amiram Eldar_, Feb 07 2020 *)
%o A112763 (Magma) [1] cat [Min(PrimeDivisors(k)): k in [2..1500]| PrimeDivisors(k) subset [2, 3, 5]]; // _Marius A. Burtea_, Feb 07 2020
%Y A112763 Cf. A020639, A051037, A086410, A112755, A112764, A188425, A188426, A188427.
%K A112763 nonn
%O A112763 1,2
%A A112763 _Reinhard Zumkeller_, Sep 18 2005