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Revision History for A245779

(Bold, blue-underlined text is an addition; faded, red-underlined text is a ~~deletion~~.)
Showing entries 1-10 | older changes

A245779

Numbers n such that (n/tau(n) - sigma(n)/n) < 1.
(history; published version)

#17 by Harvey P. Dale at Tue Nov 21 12:17:23 EST 2023

STATUS

editing

approved

#16 by Harvey P. Dale at Tue Nov 21 12:17:20 EST 2023

MATHEMATICA

Select[Range[25], #/DivisorSigma[0, #]-DivisorSigma[1, #]/#<1&] (* Harvey P. Dale, Nov 21 2023 *)

STATUS

approved

editing

#15 by Charles R Greathouse IV at Thu Sep 08 08:46:09 EDT 2022

PROG

(MAGMAMagma) [n:n in [1..1000000] | (Numerator((n /(#[d: d in Divisors(n)]))-(SumOfDivisors(n)/n))) / (Denominator((n/(#[d: d in Divisors(n)]))-(SumOfDivisors(n)/n))) lt 1]

Discussion

Thu Sep 08

08:46

OEIS Server: https://oeis.org/edit/global/2944

#14 by N. J. A. Sloane at Wed Aug 13 16:40:32 EDT 2014

STATUS

proposed

approved

#13 by Michel Marcus at Fri Aug 08 12:02:13 EDT 2014

STATUS

editing

proposed

Discussion

Sat Aug 09

15:28

Jaroslav Krizek: OK

15:50

Jaroslav Krizek: For n = 30; n/tau(n) - sigma(n)/n = 27/20 > 1.

#12 by Michel Marcus at Fri Aug 08 12:01:32 EDT 2014

NAME

Numbers n such that k(n) = (n / tau(n) - sigma(n) / n) < 1.

COMMENTS

Numbers n such that A245776(n) / A245777(n) = n / A000005(n) - A000203(n) / n < 1.

EXAMPLE

24 is in sequence because 24 / tau(24) - sigma(24) / 24 = 24 / 8 - 60 / 24 = 1/2.

MATHEMATICA

Select[Range[n],

STATUS

proposed

editing

Discussion

Fri Aug 08

12:02

Michel Marcus: Simplified definition

#11 by Michael De Vlieger at Thu Aug 07 23:45:39 EDT 2014

STATUS

editing

proposed

#10 by Michael De Vlieger at Thu Aug 07 23:43:47 EDT 2014

MATHEMATICA

a245779[n_Integer] :=

Select[Range[n],

If[#/DivisorSigma[0, #] - DivisorSigma[1, #]/# < 1, True, False] &]; a245779[1000] (* Michael De Vlieger, Aug 07 2014 *)

STATUS

proposed

editing

Discussion

Thu Aug 07

23:45

Michael De Vlieger: Doesn't this resemble the data of A020490 phi(n) <= sigma_0(n) = {1, 2, 3, 4, 6, 8, 10, 12, 18, 24, 30}? (A favorite sequence of mine). Added Mathematica.

#9 by Derek Orr at Sun Aug 03 15:55:19 EDT 2014

STATUS

editing

proposed

Discussion

Sun Aug 03

15:57

Michel Marcus: I think x/y - z/t would be more readable than x / y - z / t.

#8 by Derek Orr at Sun Aug 03 15:55:11 EDT 2014

PROG

for(n=1, 10^3, if(n/sigmanumdiv(n, 0) - sigma(n)/n < 1, print1(n, ", "))) \\ Derek Orr, Aug 02 2014

STATUS

proposed

editing