A200810 Iterate k -> d(k) until an odd prime is reached.

3, 3, 5, 3, 7, 3, 3, 3, 11, 3, 13, 3, 3, 5, 17, 3, 19, 3, 3, 3, 23, 3, 3, 3, 3, 3, 29, 3, 31, 3, 3, 3, 3, 3, 37, 3, 3, 3, 41, 3, 43, 3, 3, 3, 47, 3, 3, 3, 3, 3, 53, 3, 3, 3, 3, 3, 59, 3, 61, 3, 3, 7, 3, 3, 67, 3, 3, 3, 71, 3, 73, 3, 3, 3, 3, 3, 79, 3, 5, 3, 83

Offset: 3

Author

Charles R Greathouse IV, Nov 23 2011

Keywords

• nonn

Comments

Csajbók and Kasza call this "lasttau(n)". Imre Kátai asks for its asymptotic behavior.

Links

• Charles R Greathouse IV, Table of n, a(n) for n = 3..10000
• Tímea Csajbók and János Kasza, Iterating the tau-function, Annales Univ. Sci. Budapest., Sec. Math. 35 (2011), pp. 83-93.

Crossrefs

Cf. A200811, A200815.

Programs

PARI

a(n)=while(!isprime(n),n=numdiv(n));n \\ Charles R Greathouse IV, Nov 23 2011