%N Numbers n such that the number of even divisors of n is an even divisor of n.
%C All terms are even, since odd numbers, even if they have an even count of divisors, don't have any even divisors.
%C Includes all numbers of the form A000040(m)*A001146(n).
%H Amiram Eldar, <a href="/A181794/b181794.txt">Table of n, a(n) for n = 1..10000</a>
%e a(4)=12 has four even divisors (2, 4, 6, and 12), and 4 is one of those even divisors.
%e The number 21 is not in this sequence: it has four divisors (1, 3, 7, and 21), and 4 is not one of those divisors.
%t Select[Range[2, 1000, 2], EvenQ[DivisorSigma[0, #/2]] && MemberQ[Divisors[#], DivisorSigma[0, #/2]] &]
%t Select[Range[2, 278, 2], EvenQ[(d = DivisorSigma[0, #/2])] && Divisible[#, d] &] (* _Amiram Eldar_, Aug 29 2019 *)
%Y A100484 and A001749 are subsequences. A001146 and A100042 are also subsequences except for their initial terms.
%Y See also A033950, A049439, A181795.
%A _Matthew Vandermast_, Nov 14 2010
%E Verified and edited by _Alonso del Arte_, Nov 17 2010