The On-Line Encyclopedia of Integer Sequences (OEIS)

Revision History for A069579 (Bold, blue-underlined text is an addition; faded, red-underlined text is a ~~deletion~~.)
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A069579

Numbers k such that phi(core(k)) = core(phi(k)) where core(k) is the squarefree part of k (the smallest integer such that k*core(k) is a square).
(history; published version)

#11 by Joerg Arndt at Thu Sep 03 06:41:00 EDT 2020

STATUS

reviewed

approved

#10 by Michel Marcus at Thu Sep 03 04:35:48 EDT 2020

STATUS

proposed

reviewed

#9 by Amiram Eldar at Thu Sep 03 04:27:33 EDT 2020

STATUS

editing

proposed

#8 by Amiram Eldar at Thu Sep 03 04:03:54 EDT 2020

LINKS

Amiram Eldar, <a href="/A069579/b069579.txt">Table of n, a(n) for n = 1..10000</a>

#7 by Amiram Eldar at Thu Sep 03 04:03:29 EDT 2020

NAME

Numbers k such that phi(core(nk)) = core(phi(nk)) where core(xk) is the squarefree part of x; k (the smallest integer such that xk*core(xk) is a square).

MATHEMATICA

core[n_] := Times @@ (First[#]^Mod[Last[#], 2]& /@ FactorInteger[n]); Select[Range[300], core[EulerPhi[#]] == EulerPhi[core[#]] &] (* Amiram Eldar, Sep 03 2020 *)

CROSSREFS

Cf. A000010, A007913.

STATUS

approved

editing

#6 by Russ Cox at Fri Mar 30 18:38:57 EDT 2012

AUTHOR

_Benoit Cloitre (benoit7848c(AT)orange.fr), _, Apr 18 2002

Discussion

Fri Mar 30

18:38

OEIS Server: https://oeis.org/edit/global/216

#5 by N. J. A. Sloane at Tue Jun 01 03:00:00 EDT 2010

NAME

phi(core(n))=core(phi(n)) where core(x) is the square-free squarefree part of x; the smallest integer such that x*core(x) is a square.

KEYWORD

easy,nonn,new

#4 by N. J. A. Sloane at Sun Jun 29 03:00:00 EDT 2008

KEYWORD

easy,nonn,new

AUTHOR

Benoit Cloitre (abmtbenoit7848c(AT)wanadooorange.fr), Apr 18 2002

#3 by N. J. A. Sloane at Wed Sep 21 03:00:00 EDT 2005

KEYWORD

easy,nonn,new

AUTHOR

Benoit Cloitre (abcloitreabmt(AT)modulonetwanadoo.fr), Apr 18 2002

#2 by N. J. A. Sloane at Tue Jul 19 03:00:00 EDT 2005

KEYWORD

easy,nonn,new

AUTHOR

Benoit Cloitre (abcloitre(AT)wanadoomodulonet.fr), Apr 18 2002