A075424 a(n) = A075423(A075423(n)).

0, 1, 0, 1, 4, 5, 0, 1, 2, 9, 4, 5, 12, 13, 0, 1, 4, 5, 2, 9, 20, 21, 4, 1, 4, 1, 12, 13, 28, 29, 0, 1, 32, 33, 4, 5, 36, 37, 2, 9, 40, 41, 20, 13, 14, 45, 4, 5, 2, 9, 4, 25, 4, 5, 12, 13, 56, 57, 28, 29, 60, 9, 0, 1, 64, 65, 32, 33, 68, 69, 4, 5, 72, 13, 36, 37, 76, 77, 2, 1, 2, 81, 40, 41

Offset

2,5

Comments

From Robert Israel, Apr 11 2019: (Start)

a(n) == n (mod 2).

a(n) = 0 iff n is in A000079.

a(n) = n-2 iff n-1 is in A007674. (End)

Links

Robert Israel, Table of n, a(n) for n = 2..10000

Maple

A075423:= n -> convert(numtheory:-factorset(n), `*`)-1:
map(A075423@@2, [$2..100]); # Robert Israel, Apr 11 2019

Mathematica

A075424[n_] := Nest[Times @@ FactorInteger[#][[All, 1]] - 1 &, n, 2];
Array[A075424, 100, 2] (* Paolo Xausa, Oct 07 2025 *)

Crossrefs

Cf. A000079, A007674, A075423, A075425.

Sequence in context: A262400 A387200 A389291 * A200619 A199621 A199390

Adjacent sequences: A075421 A075422 A075423 * A075425 A075426 A075427

Keyword

nonn,look

Author

Reinhard Zumkeller, Sep 15 2002

Status

approved