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%I #5 Jan 09 2024 16:56:18
%S 9,21,25,33,49,57,69,85,93,121,129,133,145,161,169,177,185,201,205,
%T 209,213,217,221,237,249,253,265,289,305,309,315,321,341,361,365,377,
%U 381,393,413,417,437,445,453,469,485,489,493,495,497,501,505,517,529,537,545,553,565,573,597,633,649,669,681,685,689
%N Numbers whose arithmetic derivative (A003415) is a squarefree number of the form 4k+2.
%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 isA368696(n) = { my(d=A003415(n)); ((2==(d%4))&&issquarefree(d)); };
%Y Intersection of A327862 and A328393.
%Y Cf. A003415, A005117, A368697 (subsequence).
%K nonn
%O 1,1
%A _Antti Karttunen_, Jan 09 2024