|
%I #6 Oct 19 2019 10:47:24
%S 2,3,5,6,7,9,10,11,13,17,18,19,21,22,23,25,26,29,30,31,33,34,37,38,41,
%T 42,43,45,47,49,53,57,58,59,61,62,63,66,67,69,70,71,73,74,75,78,79,82,
%U 83,85,89,90,93,97,98,101,102,103,105,106,107,109,110,113,114,117,118,121,126,127,129,130,131,133,134,137,139,142
%N Numbers whose arithmetic derivative (A003415) is a squarefree number (A005117).
%H Antti Karttunen, <a href="/A328393/b328393.txt">Table of n, a(n) for n = 1..10000</a>
%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 isA328393(n) = issquarefree(A003415(n));
%Y Union of A000040 and A328234. Complement of A328303.
%Y Cf. A005117, A008966, A003415.
%Y Cf. A328252 (nonsquarefree terms), A157037, A192192, A327978 (other subsequences).
%K nonn
%O 1,1
%A _Antti Karttunen_, Oct 19 2019
|
