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A195758 Lesser prime factor of n-th Blum number.

%I A195758 #14 Dec 10 2024 05:23:27
%S A195758 3,3,3,3,7,3,3,7,3,7,3,3,11,3,7,3,3,11,7,3,3,7,11,3,3,7,3,19,3,7,11,3,
%T A195758 7,3,11,3,7,3,7,19,3,3,11,3,3,23,3,7,11,7,3,11,3,3,19,3,11,7,19,11,7,
%U A195758 3,3,7,23,3,3,7,3,23,3,19,11,3,7,3,7,11,7,3
%N A195758 Lesser prime factor of n-th Blum number.
%H A195758 Reinhard Zumkeller, <a href="/A195758/b195758.txt">Table of n, a(n) for n = 1..10000</a>
%H A195758 Wikipedia, <a href="http://en.wikipedia.org/wiki/Blum_integer">Blum integer</a>
%F A195758 a(n) * A195759(n) = A016105(n); a(n) < A195759(n);
%F A195758 a(n) = A020639(A016105(n)).
%t A195758 Take[Transpose[SortBy[{#[[1]],#[[2]],#[[1]]#[[2]]}&/@With[{c=Select[ 4*Range[ 0,200]+3,PrimeQ]},Subsets[c,{2}]],Last]][[1]],90] (* _Harvey P. Dale_, May 20 2012 *)
%o A195758 (Haskell)
%o A195758 a195758 = a020639 . a016105
%Y A195758 Cf. A096916.
%K A195758 nonn
%O A195758 1,1
%A A195758 _Reinhard Zumkeller_, Sep 23 2011