The On-Line Encyclopedia of Integer Sequences (OEIS)

Revision History for A074247 (Bold, blue-underlined text is an addition; faded, red-underlined text is a ~~deletion~~.)
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A074247

Numbers n such that harmonic mean of the divisors of n is a prime.
(history; published version)

#12 by Giovanni Resta at Mon Sep 30 04:23:13 EDT 2019

STATUS

reviewed

approved

#11 by Michel Marcus at Mon Sep 30 04:18:32 EDT 2019

STATUS

proposed

reviewed

#10 by Amiram Eldar at Mon Sep 30 04:01:41 EDT 2019

STATUS

editing

proposed

#9 by Amiram Eldar at Mon Sep 30 03:09:25 EDT 2019

LINKS

Amiram Eldar, <a href="/A074247/b074247.txt">Table of n, a(n) for n = 1..103</a> (calculated from the b-file at A001599)

#8 by Amiram Eldar at Mon Sep 30 03:08:35 EDT 2019

DATA

6, 28, 140, 496, 2970, 8128, 27846, 105664, 117800, 237510, 539400, 1421280, 1539720, 2290260, 4358600, 8872200, 33550336, 50401728, 90409410, 233103780, 287425800, 318177800, 423184320, 559903400, 825120800, 1632825792, 2705020500, 3209343200, 3328809120, 4720896180

LINKS

Amiram Eldar, <a href="/A074247/b074247.txt">Table of n, a(n) for n = 1..103</a>

EXTENSIONS

More terms from Amiram Eldar, Sep 30 2019

STATUS

approved

editing

#7 by Harvey P. Dale at Wed Jul 24 19:03:33 EDT 2019

STATUS

editing

approved

#6 by Harvey P. Dale at Wed Jul 24 19:03:31 EDT 2019

MATHEMATICA

Select[Range[1600000], PrimeQ[HarmonicMean[Divisors[#]]]&] (* Harvey P. Dale, Jul 24 2019 *)

STATUS

approved

editing

#5 by N. J. A. Sloane at Tue Feb 11 19:05:29 EST 2014

AUTHOR

_Joseph L. Pe (joseph_l_pe(AT)hotmail.com), _, Sep 20 2002

Discussion

Tue Feb 11

19:05

OEIS Server: https://oeis.org/edit/global/2119

#4 by Russ Cox at Fri Mar 30 17:34:50 EDT 2012

EXTENSIONS

a(8)-a(26) from _Donovan Johnson (donovan.johnson(AT)yahoo.com), _, Jun 10 2010

Discussion

Fri Mar 30

17:34

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

#3 by N. J. A. Sloane at Sun Jul 11 03:00:00 EDT 2010

DATA

KEYWORD

nonn,new

nonn

EXTENSIONS

a(8)-a(26) from Donovan Johnson (donovan.johnson(AT)yahoo.com), Jun 10 2010