The On-Line Encyclopedia of Integer Sequences (OEIS)

Revision History for A175522

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A175522

A000120-perfect numbers.
(history; published version)

#49 by Alois P. Heinz at Thu Feb 25 21:19:18 EST 2021

STATUS

proposed

approved

#48 by Michael S. Branicky at Thu Feb 25 18:17:56 EST 2021

STATUS

editing

proposed

#47 by Michael S. Branicky at Thu Feb 25 18:17:44 EST 2021

PROG

(Python)

from sympy import divisors

def A000120(n): return bin(n).count('1')

def aupto(limit):

alst = []

for m in range(1, limit+1):

if A000120(m) == sum(A000120(d) for d in divisors(m)[:-1]): alst += [m]

return alst

print(aupto(1563)) # Michael S. Branicky, Feb 25 2021

STATUS

approved

editing

#46 by OEIS Server at Mon Dec 14 05:20:34 EST 2020

LINKS

Amiram Eldar, <a href="/A175522/b175522_1.txt">Table of n, a(n) for n = 1..10000</a> (terms 1..1000 from Reinhard Zumkeller)

#45 by Joerg Arndt at Mon Dec 14 05:20:34 EST 2020

STATUS

reviewed

approved

Discussion

Mon Dec 14

05:20

OEIS Server: Installed new b-file as b175522.txt.  Old b-file is now b175522_1.txt.

#44 by Michel Marcus at Mon Dec 14 02:31:56 EST 2020

STATUS

proposed

reviewed

#43 by Amiram Eldar at Mon Dec 14 01:50:30 EST 2020

STATUS

editing

proposed

#42 by Amiram Eldar at Mon Dec 14 01:48:53 EST 2020

MATHEMATICA

binw[n_] := DigitCount[n, 2, 1]; Select[Range[1500], binw[#] == DivisorSum[#, binw[#1] &]/2 &] (* Amiram Eldar, Dec 14 2020 *)

#41 by Amiram Eldar at Mon Dec 14 01:37:24 EST 2020

LINKS

Amiram Eldar, <a href="/A175522/b175522_1.txt">Table of n, a(n) for n = 1..10000</a> (terms 1..1000 from Reinhard Zumkeller)

#40 by Amiram Eldar at Mon Dec 14 01:37:04 EST 2020

LINKS

Reinhard Zumkeller, Amiram Eldar, <a href="/A175522/b175522_1.txt">Table of n, a(n) for n = 1..100010000</a>

STATUS

approved

editing