A075423 a(n) = rad(n) - 1, where rad(n) is the squarefree kernel of n (A007947).

0, 1, 2, 1, 4, 5, 6, 1, 2, 9, 10, 5, 12, 13, 14, 1, 16, 5, 18, 9, 20, 21, 22, 5, 4, 25, 2, 13, 28, 29, 30, 1, 32, 33, 34, 5, 36, 37, 38, 9, 40, 41, 42, 21, 14, 45, 46, 5, 6, 9, 50, 25, 52, 5, 54, 13, 56, 57, 58, 29, 60, 61, 20, 1, 64, 65, 66, 33, 68, 69, 70, 5, 72, 73, 14, 37, 76, 77

Offset

1,3

Comments

a(n) < n for all n, see A075425.

Links

Paolo Xausa, Table of n, a(n) for n = 1..10000

Formula

A075424(n) = a(a(n)) for n>1.

Mathematica

A075423[n_] := Times @@ FactorInteger[n][[All, 1]] - 1;
Array[A075423, 100] (* Paolo Xausa, Oct 07 2025 *)

Prog

(PARI) a(n)=factorback(factor(n)[, 1])-1 \\ Charles R Greathouse IV, Jul 09 2013

Crossrefs

Cf. A007947, A075424, A075425.

Sequence in context: A197011 A326060 A321794 * A144774 A326056 A365689

Adjacent sequences: A075420 A075421 A075422 * A075424 A075425 A075426

Keyword

nonn

Author

Reinhard Zumkeller, Sep 15 2002

Status

approved