The On-Line Encyclopedia of Integer Sequences (OEIS)

Revision History for A175729 (Bold, blue-underlined text is an addition; faded, red-underlined text is a ~~deletion~~.)
Showing entries 1-10 | older changes

A175729

Numbers n such that the sum of the prime factors with multiplicity of n divides n-1.
(history; published version)

#22 by Joerg Arndt at Fri Sep 30 10:48:56 EDT 2022

STATUS

reviewed

approved

#21 by Michel Marcus at Fri Sep 30 10:45:09 EDT 2022

STATUS

proposed

reviewed

#20 by Michael S. Branicky at Fri Sep 30 10:43:36 EDT 2022

STATUS

editing

proposed

#19 by Michael S. Branicky at Fri Sep 30 10:43:34 EDT 2022

PROG

(Python)

from sympy import factorint

def ok(n): return n>1 and (n-1)%sum(p*e for p, e in factorint(n).items())==0

print([k for k in range(10**4) if ok(k)]) # Michael S. Branicky, Sep 30 2022

STATUS

approved

editing

#18 by Charles R Greathouse IV at Thu Sep 08 08:45:51 EDT 2022

PROG

(MAGMAMagma) [k:k in [2..6200]| IsIntegral((k-1)/( &+[m[1]*m[2]: m in Factorization(k)]))]; // Marius A. Burtea, Sep 16 2019

Discussion

Thu Sep 08

08:45

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

#17 by Bruno Berselli at Mon Sep 16 04:09:35 EDT 2019

STATUS

proposed

approved

#16 by Marius A. Burtea at Mon Sep 16 03:00:54 EDT 2019

STATUS

editing

proposed

#15 by Marius A. Burtea at Mon Sep 16 03:00:37 EDT 2019

PROG

(MAGMA) [k:k in [2..6200]| IsIntegral((k-1)/( &+[m[1]*m[2]: m in Factorization(k)]))]; // Marius A. Burtea, Sep 16 2019

STATUS

proposed

editing

#14 by Michel Marcus at Mon Sep 16 02:45:54 EDT 2019

STATUS

editing

proposed

#13 by Michel Marcus at Mon Sep 16 02:45:49 EDT 2019

EXAMPLE

For example, 21=7x3, 7+3=10 which divides 21-1=20.

STATUS

proposed

editing