The On-Line Encyclopedia of Integer Sequences (OEIS)

Revision History for A063507

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A063507

Least k such that k - phi(k) = n, or 0 if no such k exists.
(history; published version)

#19 by Bruno Berselli at Fri Jan 12 02:52:48 EST 2018

STATUS

reviewed

approved

#18 by Michel Marcus at Fri Jan 12 00:36:43 EST 2018

STATUS

proposed

reviewed

#17 by Michael De Vlieger at Thu Jan 11 23:14:25 EST 2018

STATUS

editing

proposed

#16 by Michael De Vlieger at Thu Jan 11 23:14:21 EST 2018

MATHEMATICA

Table[SelectFirst[Range[n^2 + 1], # - EulerPhi[#] == n &] /. k_ /; ! IntegerQ@ k -> 0, {n, 67}] (* Michael De Vlieger, Jan 11 2018 *)

STATUS

proposed

editing

#15 by M. F. Hasler at Thu Jan 11 08:56:31 EST 2018

STATUS

editing

proposed

#14 by M. F. Hasler at Thu Jan 11 08:55:55 EST 2018

CROSSREFS

Cf. A063748 (greatest solution to x-phi(x)=n).

Cf. A063740 (number of k such that cototient(k) = n).

STATUS

approved

editing

Discussion

Thu Jan 11

08:56

M. F. Hasler: none of the relevant seq. referenced that one!

#13 by Bruno Berselli at Mon Feb 02 03:50:53 EST 2015

STATUS

reviewed

approved

#12 by Joerg Arndt at Mon Feb 02 03:48:50 EST 2015

STATUS

proposed

reviewed

#11 by Michel Marcus at Mon Feb 02 01:00:31 EST 2015

STATUS

editing

proposed

#10 by Michel Marcus at Mon Feb 02 01:00:23 EST 2015

COMMENTS

If a(n) > 0, then it appears that a(n) > 1.26n. - _T. D. Noe_, Dec 06 2006

FORMULA

a(n)-A051953(a(n)) = n if possible and a(n)=0 if n belongs to A005278.

EXTENSIONS

Edited by N. J. A. Sloane, Oct 25 2008 at the suggestion of _R. J. Mathar._

STATUS

approved

editing