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%I #11 Oct 11 2019 16:56:39
%S 14,46,50,65,77,86,94,99,122,125,138,146,207,230,302,334,343,346,375,
%T 426,531,546,554,581,590,626,662,682,686,710,717,718,725,734,747,750,
%U 819,842,869,875,931,965,1002,1041,1083,1130,1145,1146,1166,1175,1202,1241,1265,1310,1331,1337,1349,1375,1418,1461,1466,1469,1501,1529,1541
%N Numbers whose second arithmetic derivative (A068346) is a squarefree number (A005117), but the first derivative (A003415) is not.
%H Antti Karttunen, <a href="/A328245/b328245.txt">Table of n, a(n) for n = 1..10000</a>
%e For n = 14, its first arithmetic derivative, A003415(14) = 9 = 3^2 is not squarefree, while the second arithmetic derivative, A003415(9) = 6 = 2* 3 is, thus 14 is included in this sequence.
%o (PARI)
%o A003415(n) = if(n<=1, 0, my(f=factor(n)); n*sum(i=1, #f~, f[i, 2]/f[i, 1]));
%o isA328245(n) = { my(u=A003415(n)); (!issquarefree(u) && issquarefree(A003415(u))); }; \\ issquarefree(0) returns 0 as zero is not considered as a squarefree number.
%Y Cf. A003415, A005117, A008966, A068346.
%Y Setwise difference A328244 \ A328234.
%Y Cf. A328253 (a subsequence, nonsquarefree terms).
%K nonn
%O 1,1
%A _Antti Karttunen_, Oct 11 2019
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