191052domain: NAppears in sequences(-1)-sigma super perfect numbers: (-1)sigma((-1)sigma(x))=2*x, where if x=Product p(i)^r(i) then (-1)sigma(x)=Product (-1+Sum p(i)^s(i), s(i)=1 to r(i)); (-1)sigma(1)=1.at n=6A051153