121486365domain: NAppears in sequences(+2)-unitary sigma 3-multiple perfect number: numbers k such that (+2)usigma(k) = 3*k, where (+2)usigma(k) = A107759(k).at n=4A054862Numbers k such that Sum_{d|k} tau(d)/d is an integer, where tau(x) = A000005(x).at n=13A068978