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A356018 a(n) is the number of evil divisors (A001969) of n.

%I A356018 #28 Aug 07 2022 08:39:19
%S A356018 0,0,1,0,1,2,0,0,2,2,0,3,0,0,3,0,1,4,0,3,1,0,1,4,1,0,3,0,1,6,0,0,2,2,
%T A356018 1,6,0,0,2,4,0,2,1,0,5,2,0,5,0,2,3,0,1,6,1,0,2,2,0,9,0,0,3,0,2,4,0,3,
%U A356018 2,2,1,8,0,0,4,0,1,4,0,5,3,0,1,3,3,2
%N A356018 a(n) is the number of evil divisors (A001969) of n.
%C A356018 a(n) = 0 iff n is in A093696.
%F A356018 a(n) = A000005(n) - A227872(n).
%e A356018 12 has 6 divisors: {1, 2, 3, 4, 6, 12} of which three {3, 6, 12} have an even number of 1's in their binary expansion with 11, 110 and 11100 respectively; hence a(12) = 3.
%p A356018 A356018 := proc(n)
%p A356018     local a,d ;
%p A356018     a := 0 ;
%p A356018     for d in numtheory[divisors](n) do
%p A356018         if isA001969(d) then
%p A356018             a := a+1 ;
%p A356018         end if;
%p A356018     end do:
%p A356018     a ;
%p A356018 end proc:
%p A356018 seq(A356018(n),n=1..200) ;  # _R. J. Mathar_, Aug 07 2022
%t A356018 a[n_] := DivisorSum[n, 1 &, EvenQ[DigitCount[#, 2, 1]] &]; Array[a, 100] (* _Amiram Eldar_, Jul 23 2022 *)
%o A356018 (Python)
%o A356018 from sympy import divisors
%o A356018 def c(n): return bin(n).count("1")&1 == 0
%o A356018 def a(n): return sum(1 for d in divisors(n, generator=True) if c(d))
%o A356018 print([a(n) for n in range(1, 101)]) # _Michael S. Branicky_, Jul 23 2022
%o A356018 (PARI) a(n) = my(v = valuation(n, 2)); n>>=v; d=divisors(n); sum(i=1, #d, bitand(hammingweight(d[i]), 1) == 0) * (v+1) \\ _David A. Corneth_, Jul 23 2022
%Y A356018 Cf. A000005, A001969, A093688, A093696 (location of 0s), A227872, A356019, A356020.
%Y A356018 Similar sequences: A083230, A087990, A087991, A332268, A355302.
%K A356018 nonn,easy,base
%O A356018 1,6
%A A356018 _Bernard Schott_, Jul 23 2022
%E A356018 More terms from _David A. Corneth_, Jul 23 2022