The On-Line Encyclopedia of Integer Sequences (OEIS)

Revision History for A110590

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A110590

Balanced numbers n (A020492) such that phi(n) is not divisible by 12.
(history; published version)

#14 by Bruno Berselli at Mon Jul 13 06:56:04 EDT 2015

STATUS

proposed

approved

#13 by Giovanni Resta at Mon Jul 13 05:29:04 EDT 2015

STATUS

editing

proposed

#12 by Giovanni Resta at Mon Jul 13 05:28:39 EDT 2015

COMMENTS

a(11) if it exists is greater than 10^13. - Giovanni Resta, Jul 13 2015

STATUS

approved

editing

#11 by Joerg Arndt at Tue Aug 06 09:54:34 EDT 2013

STATUS

editing

approved

#10 by Joerg Arndt at Tue Aug 06 09:54:28 EDT 2013

FORMULA

n such that sigma(n)/phi(n) is an integer and phi(n) mod 12 > != 0.

#9 by Joerg Arndt at Tue Aug 06 09:54:02 EDT 2013

KEYWORD

nonn,more,changed

#8 by Joerg Arndt at Tue Aug 06 09:53:29 EDT 2013

FORMULA

n such that sigma(n)/phi(n) is an integer and phi(n) mod 12 > 0.

MAPLE

with(numtheory): BNM:=[]: for z from 1 to 1 do for n from 1 to 100000 do if phi(n) mod 12 > 0 and sigma(n) mod phi(n) = 0 then BNM:=[op(BNM), n] fi; od; od; BNM; # after 3828 there no others out up to 2*10^6.

MATHEMATICA

fQ[n_] := Block[{ds = DivisorSigma[1, n], ep = EulerPhi@n}, Mod[ep, 12] > 0 && IntegerQ[ds/ep]]; Do[ If[ fQ@n, Print@n], {n, 4*10^8}] (from _* _Robert G. Wilson v_, Jun 19 2006 *)

STATUS

proposed

editing

#7 by Michel Marcus at Tue Aug 06 07:45:15 EDT 2013

STATUS

editing

proposed

#6 by Michel Marcus at Tue Aug 06 07:45:08 EDT 2013

COMMENTS

a(11) if it exists is greater than 10^8. - Michel Marcus, Aug 06 2013

STATUS

approved

editing

#5 by Charles R Greathouse IV at Sat Jul 14 11:40:53 EDT 2012

MATHEMATICA

fQ[n_] := Block[{ds = DivisorSigma[1, n], ep = EulerPhi@n}, Mod[ep, 12] > 0 && IntegerQ[ds/ep]]; Do[ If[ fQ@n, Print@n], {n, 4*10^8}] (from _Robert G. Wilson v (rgwv(at)rgwv.com), _, Jun 19 2006)

Discussion

Sat Jul 14

11:40

OEIS Server: https://oeis.org/edit/global/1816