3961980

Appears 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=9A051153
• a(n) = (n+1)*(n+2)*(n+3)*(n+4)*(19*n^2 + 47*n + 30)/720.at n=21A108677