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%I #12 Mar 23 2017 10:37:56
%S 0,0,0,2,0,5,0,3,3,7,0,2,0,3,2,2,0,7,0,3,5,13,0,11,5,5,3,2,0,31,0,5,7,
%T 19,3,5,0,7,2,17,0,41,0,3,13,5,0,7,7,5,5,7,0,3,2,23,11,31,0,23,0,11,
%U 17,3,3,61,0,3,13,59,0,13,0,13,11,5,3,71,0,11,3,43,0,31,11,5,2,7,0,41,5,3
%N Largest prime factor of arithmetic derivative of n if it exists, or a(n)=0 for n=1 and n=prime.
%H Floris P. van Doorn and Jasper Mulder, <a href="/A086131/b086131.txt">Table of n, a(n) for n = 1..20000</a>
%p with(numtheory):
%p d:= n-> n*add(i[2]/i[1], i=ifactors(n)[2]):
%p a:= n-> (f-> `if`(f<2, 0, max(factorset(f)[])))(d(n)):
%p seq(a(n), n=1..105); # _Alois P. Heinz_, Jun 08 2015
%t d[n_] := n*Sum[i[[2]]/i[[1]], {i, FactorInteger[n]}];
%t a[n_] := Function[f, If[f<2, 0, Max[FactorInteger[f][[All, 1]]]]][d[n]];
%t Table[a[n], {n, 1, 105}] (* _Jean-François Alcover_, Mar 23 2017, after _Alois P. Heinz_ *)
%Y Cf. A003415.
%K nonn
%O 1,4
%A _Labos Elemer_, Jul 23 2003
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