The On-Line Encyclopedia of Integer Sequences (OEIS)

Revision History for A087708 (Bold, blue-underlined text is an addition; faded, red-underlined text is a ~~deletion~~.)
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A087708

First integer > n reached under iteration of map x -> (5/3)*ceiling(x) when started at n, or -1 if no such integer is ever reached.
(history; published version)

#11 by Andrew Howroyd at Sat Sep 02 16:59:00 EDT 2023

STATUS

reviewed

approved

#10 by Michel Marcus at Sat Sep 02 13:29:57 EDT 2023

STATUS

proposed

reviewed

#9 by Chai Wah Wu at Sat Sep 02 11:19:46 EDT 2023

STATUS

editing

proposed

#8 by Chai Wah Wu at Sat Sep 02 11:19:42 EDT 2023

PROG

return int(x) # Chai Wah Wu, Sep 02 2023

#7 by Chai Wah Wu at Sat Sep 02 11:19:29 EDT 2023

PROG

(Python)

from fractions import Fraction

def A087708(n):

x = Fraction(n)

while x.denominator > 1 or x<=n:

x = Fraction(5*x.__ceil__(), 3)

return int(x) # Chai Wah Wu, Sep 02 2023

STATUS

approved

editing

#6 by Charles R Greathouse IV at Thu Oct 04 10:28:48 EDT 2012

LINKS

J. C. Lagarias and N. J. A. Sloane, Approximate squaring (<a href="http://www.research.attneilsloane.com/~njas/doc/apsq.pdf">pdf</a>, <a href="http://www.research.attneilsloane.com/~njas/doc/apsq.ps">ps</a>), Experimental Math., 13 (2004), 113-128.

Discussion

Thu Oct 04

10:28

OEIS Server: https://oeis.org/edit/global/1833

#5 by Russ Cox at Fri Mar 30 16:49:49 EDT 2012

AUTHOR

_N. J. A. Sloane (njas(AT)research.att.com), _, Sep 29 2003

Discussion

Fri Mar 30

16:49

OEIS Server: https://oeis.org/edit/global/110

#4 by N. J. A. Sloane at Fri Feb 27 03:00:00 EST 2009

KEYWORD

nonn,new

nonn

AUTHOR

N. J. A. Sloane (njas, (AT)research.att.com), Sep 29 2003

#3 by N. J. A. Sloane at Sun Feb 20 03:00:00 EST 2005

LINKS

J. C. Lagarias and N. J. A. Sloane, Approximate squaring (<a href="http://www.research.att.com/~njas/doc/apsq.pdf">pdf</a>, <a href="http://www.research.att.com/~njas/doc/apsq.ps">ps</a>), preprint, 2003Experimental Math., 13 (2004), 113-128.

KEYWORD

nonn,new

nonn

#2 by N. J. A. Sloane at Sat Jun 12 03:00:00 EDT 2004

MAPLE

c2 := proc(x, y) x*ceil(y); end; r := 5/3; ch := proc(x) local n, y; global r; y := c2(r, x); for n from 1 to 20 do if whattype(y) = 'integer' then RETURN([x, n, y]); else y := c2(r, y); fi; od: RETURN(['NULL', 'NULL', 'NULL']); end; [seq(ch(n)[3], n=1..100)];

KEYWORD

nonn,new

nonn