cp's OEIS Frontend

A369663 Numbers k of the form 4m+3, whose arithmetic derivative k' is of the form 4u+2, and k' has an even number of prime factors.

%I A369663 #7 Feb 06 2024 16:24:18
%S A369663 375,459,783,819,875,1071,1107,1155,1375,1395,1715,1911,1935,1995,
%T A369663 2223,2275,2375,2499,2619,2655,2695,2727,2875,2907,2943,3003,3051,
%U A369663 3135,3195,3255,3315,3519,3575,3627,3699,3843,3927,3975,4059,4459,4515,4671,4815,4887,4935,4959,5187,5247,5375,5415,5607,5635,5655
%N A369663 Numbers k of the form 4m+3, whose arithmetic derivative k' is of the form 4u+2, and k' has an even number of prime factors.
%H A369663 Antti Karttunen, <a href="/A369663/b369663.txt">Table of n, a(n) for n = 1..10000</a>
%o A369663 (PARI)
%o A369663 A003415(n) = if(n<=1, 0, my(f=factor(n)); n*sum(i=1, #f~, f[i, 2]/f[i, 1]));
%o A369663 isA369663(n) = if(3!=(n%4), 0, my(d=A003415(n)); (2==(d%4) && !(bigomega(d)%2)));
%Y A369663 Intersection of A004767 and A369661.
%Y A369663 Subsequence of A369666.
%Y A369663 Cf. A003415, A351228.
%K A369663 nonn
%O A369663 1,1
%A A369663 _Antti Karttunen_, Feb 06 2024