%I
%S 1,3,3,3,3,3,3,11,20,20,20,32,32,32,32,32,32,50,50,50,50,50,50,74,74,
%T 74,74,74,74,74,74,74,74,74,74,110,110,110,110,150,150,150,150,150,
%U 150,150,150,150,150,150,150,150,150,150,150,206,206,206,206,266
%N Sum of the refactorable numbers less than or equal to n.
%C A number is refactorable if it is divisible by the number of its divisors.
%C The first 8 terms of a(n) are odd. The next odd term after 11 is a(225) = 2395.
%F a(n) = sum( (i) * ( 1 + floor(i/d(i))  ceil(i/d(i)) ), i = 1..n ), where d(n) is the number of divisors less than or equal to n.
%p with(numtheory); a:=n>sum( (i) * ( 1 + floor(i/tau(i))  ceil(i/tau(i)) ), i = 1..n );
%Y Cf. A033950, A000005, A141586, A057265, A036896, A036898, A114617.
%K nonn
%O 1,2
%A _Wesley Ivan Hurt_, Jan 16 2013
