A200815 -id:A200815 - cp's OEIS frontend

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

Charles R Greathouse IV, Nov 23 2011

nonn

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

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.

Cf. A200811, A200815.

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

A200811 Iterate k -> d(k) until an odd prime is reached, starting from the n-th composite.

Original entry on oeis.org

3, 3, 3, 3, 3, 3, 3, 3, 5, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 7, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 5, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3

Offset: 1

Charles R Greathouse IV, Nov 23 2011

nonn

a(n) is not 3 for n in {9, 45, 58, 89, 128, 163, 168, ...}.

Charles R Greathouse IV, Table of n, a(n) for n = 1..10000
Tímea Csajbók and János Kasza, Iterating the tau-function, Annales Univ. Sci. Budapest., Sec. Math. 35 (2011), pp. 83-93.

Cf. A200810, A200815.

cp's OEIS Frontend

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

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