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%I #23 Apr 03 2020 15:06:57
%S 9,10,12,26,49,56,58,76,122,332,568,961,992,1018,2042,3344,4336,8186,
%T 16129,16256,32762,37432,82704,227744,266176,269072,299576,856544,
%U 2097146,5385812,8388602,9834772,16580864,17895664,19173944,33554426,34636768,61008020,67092481,67100672
%N Composite numbers k such that the sum of the proper divisors of k is a power of 2.
%C If m = 2^j-1 is a Mersenne prime then m^2 and m*(2^j) (twice a perfect number) are terms. If m-2 is also a prime, then 2*(m-2) is a term. - _Metin Sariyar_, Mar 31 2020
%H Giovanni Resta, <a href="/A279731/b279731.txt">Table of n, a(n) for n = 1..59</a> (terms < 4*10^12)
%e 12 is a term because 1 + 2 + 3 + 4 + 6 = 2^4.
%t Select[Range[7*10^7],CompositeQ[#]&&IntegerQ[Log[2,Total[ Most[ Divisors[ #]]]]]&] (* _Harvey P. Dale_, Apr 01 2018 *)
%o (PARI) isok(n) = ispower(sigma(n)-n,,&k) && (k==2); \\ _Michel Marcus_, Dec 18 2016
%Y Cf. A001065, A046528.
%K nonn
%O 1,1
%A _Altug Alkan_, Dec 18 2016
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