21857648640domain: NAppears in sequencesNumbers k such that sigma(k) = 7k/2.at n=5A055153Numbers m with half-integral abundancy index, sigma(m)/m = k+1/2 with integer k.at n=12A159907Numbers n such that antisigma(n) mod n = 0, where antisigma(n) = A024816(n) = sum of numbers less than n which do not divide n.at n=13A242484