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Revision History for A033620 (Bold, blue-underlined text is an addition; faded, red-underlined text is a deletion.)

Showing entries 1-10 | older changes
Numbers all of whose prime factors are palindromes.
(history; published version)
#34 by Joerg Arndt at Wed Apr 07 00:23:45 EDT 2021
STATUS

reviewed

approved

#33 by Michel Marcus at Tue Apr 06 11:18:59 EDT 2021
STATUS

proposed

reviewed

#32 by Michael S. Branicky at Tue Apr 06 11:12:32 EDT 2021
STATUS

editing

proposed

#31 by Michael S. Branicky at Tue Apr 06 11:06:45 EDT 2021
PROG

(Python)

from sympy import isprime, primefactors

def pal(n): s = str(n); return s == s[::-1]

def ok(n): return all(pal(f) for f in primefactors(n))

print(list(filter(ok, range(1, 132)))) # Michael S. Branicky, Apr 06 2021

STATUS

approved

editing

#30 by N. J. A. Sloane at Mon Sep 28 02:01:03 EDT 2020
STATUS

proposed

approved

#29 by David A. Corneth at Sun Sep 27 05:49:20 EDT 2020
STATUS

editing

proposed

#28 by David A. Corneth at Sun Sep 27 05:49:10 EDT 2020
LINKS

<a href="/index/Pri#prime_factors">Index entries sequences related to prime factors</a>

STATUS

proposed

editing

#27 by Amiram Eldar at Sun Sep 27 03:20:12 EDT 2020
STATUS

editing

proposed

#26 by Amiram Eldar at Sun Sep 27 03:14:06 EDT 2020
FORMULA

Sum_{n>=1} 1/a(n) = Product_{p in A002385} p/(p-1) = 5.0949... - Amiram Eldar, Sep 27 2020

#25 by Amiram Eldar at Sun Sep 27 03:10:52 EDT 2020
EXAMPLE

10 = 2 * 5 is a term since both 2 and 5 are palindromes.

110 = 2 * 5 * 11 is a term since 2, 5 and 11 are palindromes.