The On-Line Encyclopedia of Integer Sequences (OEIS)

Revision History for A176670

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A176670

Composite numbers having the same digits as their prime factors (with multiplicity), excluding zero digits.
(history; published version)

#54 by N. J. A. Sloane at Thu Apr 22 21:54:33 EDT 2021

STATUS

proposed

approved

#53 by Michael S. Branicky at Thu Apr 22 20:51:31 EDT 2021

STATUS

editing

proposed

#52 by Michael S. Branicky at Thu Apr 22 20:50:22 EDT 2021

DATA

1111, 1255, 12955, 17482, 25105, 28174, 51295, 81229, 91365, 100255, 101299, 105295, 107329, 110191, 110317, 117067, 124483, 127417, 129595, 132565, 137281, 145273, 146137, 149782, 163797, 171735, 174082, 174298, 174793, 174982, 193117, 208174, 210181, 217894

PROG

(Python)

from sympy import factorint, flatten

def sd(n): return sorted(str(n).replace('0', ''))

def ok(n):

f = factorint(n)

return sum(f[p] for p in f) > 1 and sd(n) == sorted(flatten(sd(p)*f[p] for p in f))

print(list(filter(ok, range(220000)))) # Michael S. Branicky, Apr 22 2021

STATUS

approved

editing

#51 by N. J. A. Sloane at Wed Jan 11 03:16:59 EST 2017

STATUS

proposed

approved

#50 by Ely Golden at Wed Jan 11 00:09:12 EST 2017

STATUS

editing

proposed

#49 by Ely Golden at Wed Jan 11 00:09:08 EST 2017

COMMENTS

Members Terms of this sequence never have more zero digits than their prime factors. - Ely Golden, Jan 10 2017

STATUS

proposed

editing

#48 by Ely Golden at Wed Jan 11 00:04:07 EST 2017

STATUS

editing

proposed

Discussion

Wed Jan 11

00:07

Michel Marcus: Or you could also say "Terms of this ...

#47 by Ely Golden at Wed Jan 11 00:04:06 EST 2017

COMMENTS

members Members of this sequence never have more zero digits than their prime factors. - Ely Golden, Jan 10 2017

STATUS

proposed

editing

#46 by Ely Golden at Tue Jan 10 23:51:06 EST 2017

STATUS

editing

proposed

#45 by Ely Golden at Tue Jan 10 23:50:32 EST 2017

COMMENTS

It seems as though members of this sequence never have more zero digits than their prime factors; however, this has not been proved. - Ely Golden, Dec 25 2016Jan 10 2017

LINKS

Ely Golden, <a href="/A280827/a280827.txt">Proof that A280827(n)>=0 for all n>1</a>

STATUS

approved

editing