usigma(usigma(n))=3*n where usigma(n) is the sum of unitary divisors of n (A034448).

A064012

usigma(usigma(n))=3*n where usigma(n) is the sum of unitary divisors of n (A034448).

Terms

    a(0) =10a(1) =30a(2) =288a(3) =660a(4) =720a(5) =2146560

External references