The On-Line Encyclopedia of Integer Sequences (OEIS)

Revision History for A309307

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A309307

Number of unitary divisors of n (excluding 1).
(history; published version)

#13 by Wesley Ivan Hurt at Fri Feb 04 22:55:42 EST 2022

STATUS

editing

approved

#12 by Wesley Ivan Hurt at Fri Feb 04 22:54:43 EST 2022

FORMULA

a(n) = -1 + Sum_{d|n} mu(d)^2. - Wesley Ivan Hurt, Feb 04 2022

STATUS

approved

editing

#11 by Joerg Arndt at Fri May 29 04:58:27 EDT 2020

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reviewed

approved

#10 by Michel Marcus at Fri May 29 04:39:01 EDT 2020

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proposed

reviewed

#9 by Amiram Eldar at Fri May 29 04:15:15 EDT 2020

STATUS

editing

proposed

#8 by Amiram Eldar at Fri May 29 04:12:08 EDT 2020

LINKS

Amiram Eldar, <a href="/A309307/b309307.txt">Table of n, a(n) for n = 1..10000</a>

STATUS

approved

editing

#7 by Vaclav Kotesovec at Wed Oct 16 07:30:33 EDT 2019

STATUS

editing

approved

#6 by Vaclav Kotesovec at Wed Oct 16 07:30:10 EDT 2019

FORMULA

Sum_{k=1..n} a(k) ~ 6*n*(log(n) + 2*gamma - 1 - Pi^2/6 - 12*zeta'(2)/Pi^2) / Pi^2, where gamma is the Euler-Mascheroni constant A001620. - Vaclav Kotesovec, Oct 16 2019

STATUS

approved

editing

#5 by Susanna Cuyler at Sun Jul 21 22:00:01 EDT 2019

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proposed

approved

#4 by Ilya Gutkovskiy at Sun Jul 21 18:01:02 EDT 2019

STATUS

editing

proposed