The On-Line Encyclopedia of Integer Sequences (OEIS)

Revision History for A267892 (Bold, blue-underlined text is an addition; faded, red-underlined text is a ~~deletion~~.)
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A267892

Numbers with 9 odd divisors.
(history; published version)

#39 by Joerg Arndt at Mon Sep 16 02:10:26 EDT 2024

STATUS

reviewed

approved

#38 by Hugo Pfoertner at Mon Sep 16 02:07:00 EDT 2024

STATUS

proposed

reviewed

#37 by Amiram Eldar at Mon Sep 16 01:07:22 EDT 2024

STATUS

editing

proposed

#36 by Amiram Eldar at Mon Sep 16 00:41:14 EDT 2024

FORMULA

Sum_{n>=1} 1/a(n) = (P(2)-1/4)^2 - P(4) + 2*P(8) + 7/128 = 0.026721189882055998428..., where P(s) is the prime zeta function. - _Amiram Eldar_, Sep 16 2024

#35 by Amiram Eldar at Mon Sep 16 00:41:00 EDT 2024

COMMENTS

Numbers n k such that the symmetric representation of sigma(nk) has 9 subparts. - Omar E. Pol, Dec 29 2016

Numbers n k such that A000265(nk) is in A030627.

FORMULA

Sum_{n>=1} 1/a(n) = (P(2)-1/4)^2 - P(4) + 2*P(8) + 7/128 = 0.026721189882055998428..., where P(s) is the prime zeta function.

STATUS

approved

editing

#34 by Harvey P. Dale at Sun May 12 15:33:43 EDT 2019

STATUS

editing

approved

#33 by Harvey P. Dale at Sun May 12 15:33:37 EDT 2019

MATHEMATICA

Select[Range[16000], Total[Boole[OddQ[Divisors[#]]]]==9&] (* Harvey P. Dale, May 12 2019 *)

STATUS

approved

editing

#32 by Giovanni Resta at Thu Aug 16 13:30:53 EDT 2018

STATUS

reviewed

approved

#31 by Michael B. Porter at Thu Aug 16 01:20:13 EDT 2018

STATUS

proposed

reviewed

#30 by Julie Jones at Wed Aug 15 01:05:46 EDT 2018

STATUS

editing

proposed