a(n) = prime reached by iterating f(x) = sigma(x)-1 starting at n, or -1 if no prime is ever reached.
A039654
a(n) = prime reached by iterating f(x) = sigma(x)-1 starting at n, or -1 if no prime is ever reached.
Terms
- a(0) =2a(1) =3a(2) =11a(3) =5a(4) =11a(5) =7a(6) =23a(7) =71a(8) =17a(9) =11a(10) =71a(11) =13a(12) =23a(13) =23a(14) =71a(15) =17a(16) =59a(17) =19a(18) =41a(19) =31a(20) =47a(21) =23a(22) =59a(23) =71a(24) =41a(25) =71a(26) =71a(27) =29a(28) =71a(29) =31
External references
- oeis: A039654