%I #18 Feb 10 2024 18:57:48

%S 9,21,25,33,49,57,69,85,93,121,129,133,145,169,177,205,213,217,237,

%T 249,253,265,289,309,329,361,375,393,417,445,459,469,473,489,493,505,

%U 517,529,533,553,565,573,581,597,629,633,669,685,697,713,753,781,783,793,813,817,819,841,865,869,875,889,913,933,949,961

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

%C Equally, numbers k whose arithmetic derivative k' is congruent to 2 modulo 4 and A276085(k') is congruent to 3 modulo 4.

%C Numbers k such that A003415(k) is in A369966.

%C For all n >= 1, A003415((1/2)*A003415(a(n))) is odd.

%H Antti Karttunen, <a href="/A369661/b369661.txt">Table of n, a(n) for n = 1..10000</a>

%o (PARI) \\ See A369660.

%Y Setwise difference A327862 \ A369662.

%Y Cf. A003415, A369660 (characteristic function), A369966.

%Y Subsequences: A108181, A369663 (terms of the form 4m+3).

%K nonn

%O 1,1

%A _Antti Karttunen_, Feb 06 2024