Number of iterations of f(x) = sigma(x)-1 applied to n required to reach a prime, or -1 if no prime is ever reached.

A039655

Number of iterations of f(x) = sigma(x)-1 applied to n required to reach a prime, or -1 if no prime is ever reached.

Terms

    a(0) =0a(1) =0a(2) =2a(3) =0a(4) =1a(5) =0a(6) =2a(7) =5a(8) =1a(9) =0a(10) =4a(11) =0a(12) =1a(13) =1a(14) =2a(15) =0a(16) =2a(17) =0a(18) =1a(19) =1a(20) =2a(21) =0a(22) =1a(23) =2a(24) =1a(25) =3a(26) =2a(27) =0a(28) =1a(29) =0

External references