%I
%S 280,34960,4960000,15887872,20527600,105056320,44781248512
%N Numbers equal to the sum of their proper divisors d such that d mod 3 = 2.
%C The numbers equal to the sum of their proper divisors which are a multiple of 3 are the perfect numbers (A000396) multiplied by 3.
%e The proper divisors of 280 which are congruent to 2 mod 3 are 2, 5, 8, 14, 20, 35, 56, and 140. Since their sum is 280, 280 is a term.
%t Select[Range[40000], # == Plus @@ Select[ Most@ Divisors[#], Mod[#, 3] == 2 &] &]
%o (PARI) is(n)=sumdiv(n, d, if(d%3==2, d, 0))==if(n%3==2, 2*n, n) \\ _Charles R Greathouse IV_, May 09 2016
%Y Cf. A272716, A000396, A078182 (sum of proper and improver divisors).
%K nonn,more
%O 1,1
%A _Giovanni Resta_, May 05 2016
