The On-Line Encyclopedia of Integer Sequences (OEIS)

Revision History for A072393

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A072393

Numbers n such that n - reverse(n) = phi(n).
(history; published version)

#13 by N. J. A. Sloane at Tue Feb 11 19:09:01 EST 2014

AUTHOR

_Joseph L. Pe (JosephL.Pe(AT)hotmail.com), _, Jul 21 2002

Discussion

Tue Feb 11

19:09

OEIS Server: https://oeis.org/edit/global/2120

#12 by N. J. A. Sloane at Sun Oct 28 13:20:28 EDT 2012

STATUS

proposed

approved

#11 by Giovanni Resta at Sun Oct 28 12:20:29 EDT 2012

STATUS

editing

proposed

#10 by Giovanni Resta at Sun Oct 28 12:20:17 EDT 2012

COMMENTS

a(51) > 10^12. - Giovanni Resta, Oct 28 2012

LINKS

Giovanni Resta, <a href="/A072393/b072393.txt">Table of n, a(n) for n = 1..50</a>

STATUS

approved

editing

#9 by Russ Cox at Fri Mar 30 17:37:41 EDT 2012

COMMENTS

If m>1 and p=2*10^m+3 is prime then n=27*p is in the sequence because n-reversal(n)=27*(2*10^m+3)-reversal(27*(2*10^m+3))= (54*10^m+81)-(18*10^m+45)=36*10^m+36=18*(2*10^m+2)=phi(27)* phi(2*10^m+3)=phi(27*(2*10^m+3))=phi(n). Also if m>2 and p=(389*10^m+109)/3 is prime then 7*p is in the sequence (the proof is easy). Next term is greater than 2*10^8. - _Farideh Firoozbakht (mymontain(AT)yahoo.com), _, Jan 27 2006

EXTENSIONS

More terms from _Farideh Firoozbakht (mymontain(AT)yahoo.com), _, Jan 27 2006

Discussion

Fri Mar 30

17:37

OEIS Server: https://oeis.org/edit/global/181

#8 by Russ Cox at Fri Mar 30 17:34:49 EDT 2012

EXTENSIONS

a(22)-a(29) from _Donovan Johnson (donovan.johnson(AT)yahoo.com), _, Dec 04 2011

Discussion

Fri Mar 30

17:34

OEIS Server: https://oeis.org/edit/global/163

#7 by T. D. Noe at Sun Dec 04 18:43:39 EST 2011

STATUS

proposed

approved

#6 by Donovan Johnson at Sun Dec 04 18:33:02 EST 2011

STATUS

editing

proposed

#5 by Donovan Johnson at Sun Dec 04 18:32:31 EST 2011

DATA

91, 874, 3411, 9093, 40112, 44252, 54081, 67284, 80224, 90933, 91503, 4961782, 5400081, 5726691, 8750834, 9076921, 9155055, 54000081, 62023914, 90766921, 93079231, 430770922, 540000081, 636355044, 808618664, 907666921, 928709013, 4050394312, 4262971312

EXTENSIONS

a(22)-a(29) from Donovan Johnson (donovan.johnson(AT)yahoo.com), Dec 04 2011

STATUS

approved

editing

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

COMMENTS

If m>1 and p=2*10^m+3 is prime then n=27*p is in the sequence because n-reversal(n)=27*(2*10^m+3)-reversal(27*(2*10^m+3))= (54*10^m+81)-(18*10^m+45)=36*10^m+36=18*(2*10^m+2)=phi(27)* phi(2*10^m+3)=phi(27*(2*10^m+3))=phi(n). Also if m>2 and p=(389*10^m+109)/3 is prime then 7*p is in the sequence (the proof is easy). Next term is greater than 2*10^8. - Farideh Firoozbakht (mymontain(AT)yahoo.com), Jan 27 2006

KEYWORD

base,nonn,new