Composite numbers k such that sigma_2(k) - 1 is a square, where sigma_2(k) = A001157(k) is the sum of squares of divisors of k.

A318169

Composite numbers k such that sigma_2(k) - 1 is a square, where sigma_2(k) = A001157(k) is the sum of squares of divisors of k.

Terms

    a(0) =6a(1) =40a(2) =136a(3) =2696a(4) =3352a(5) =46976a(6) =223736a(7) =5509736a(8) =1915798072

External references