The On-Line Encyclopedia of Integer Sequences (OEIS)

Revision History for A318875

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Showing entries 1-10 | older changes

A318875

Number of divisors d of n for which 2*phi(d) < d.
(history; published version)

#13 by Joerg Arndt at Mon Jul 08 10:40:57 EDT 2024

STATUS

reviewed

approved

#12 by Michel Marcus at Mon Jul 08 10:33:57 EDT 2024

STATUS

proposed

reviewed

#11 by Paolo Xausa at Mon Jul 08 09:34:14 EDT 2024

STATUS

editing

proposed

#10 by Paolo Xausa at Mon Jul 08 09:32:08 EDT 2024

MATHEMATICA

A318875[n_] := DivisorSum[n, 1 &, 2*EulerPhi[#] < # &];

Array[A318875, 100] (* Paolo Xausa, Jul 08 2024 *)

STATUS

approved

editing

#9 by Bruno Berselli at Wed Sep 05 11:24:06 EDT 2018

STATUS

reviewed

approved

#8 by Peter Luschny at Wed Sep 05 11:18:25 EDT 2018

STATUS

proposed

reviewed

#7 by Peter Luschny at Wed Sep 05 11:18:14 EDT 2018

STATUS

editing

proposed

#6 by Peter Luschny at Wed Sep 05 11:17:56 EDT 2018

MAPLE

A318875 := n -> nops(select(d -> (2*numtheory:-phi(d)) < d, divisors(n))):

seq(A318875(n), n=1..199); # Peter Luschny, Sep 05 2018

STATUS

proposed

editing

#5 by Antti Karttunen at Wed Sep 05 10:14:34 EDT 2018

STATUS

editing

proposed

#4 by Antti Karttunen at Wed Sep 05 10:10:47 EDT 2018

LINKS

Antti Karttunen, <a href="/A318875/b318875.txt">Table of n, a(n) for n = 1..65537</a>