The On-Line Encyclopedia of Integer Sequences (OEIS)

Revision History for A248952 (Bold, blue-underlined text is an addition; faded, red-underlined text is a ~~deletion~~.)
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A248952

Smallest term in wrecker ball sequence starting with n.
(history; published version)

#37 by Michael De Vlieger at Fri Mar 24 23:11:57 EDT 2023

STATUS

proposed

approved

#36 by Peter Luschny at Fri Mar 24 20:20:16 EDT 2023

STATUS

editing

proposed

#35 by Peter Luschny at Fri Mar 24 20:14:30 EDT 2023

PROG

(Python)

def A248952(n):

(Python) def A248952(n): return min(A248939_row(n)); // _# _M. F. Hasler_, Mar 18 2019

STATUS

approved

editing

Discussion

Fri Mar 24

20:20

Peter Luschny: Contrary to claims to the contrary, the function 'A248939_row' is very well available, only the victim of a line-saving madness favored by MFH.

#34 by Charles R Greathouse IV at Thu May 16 01:32:32 EDT 2019

LINKS

Gordon Hamilton, <a href="https://www.youtube.com/watch?v=mQdNaofLqVc&feature=youtu.be">Wrecker Ball Sequences</a>, Video, 2013

Discussion

Thu May 16

01:32

OEIS Server: https://oeis.org/edit/global/2815

#33 by OEIS Server at Tue Mar 19 00:10:58 EDT 2019

LINKS

M. F. Hasler, <a href="/A248952/b248952_1.txt">Table of n, a(n) for n = 0..5000</a> (first 1000 terms from Reinhard Zumkeller), Mar 19 2019

#32 by N. J. A. Sloane at Tue Mar 19 00:10:58 EDT 2019

STATUS

editing

approved

Discussion

Tue Mar 19

00:10

OEIS Server: Installed new b-file as b248952.txt.  Old b-file is now b248952_1.txt.

#31 by N. J. A. Sloane at Tue Mar 19 00:10:28 EDT 2019

COMMENTS

It is currently unproved whether all orbits are finite, and therefore unclear whether all a(n) are well defined. In particular, the orbit of n = 11281 is of unknown length > , but is certainly greater than 32*10^9 steps. - M. F. Hasler, Mar 18 2019

STATUS

proposed

editing

Discussion

Tue Mar 19

00:10

N. J. A. Sloane: I edited the last sentence a bit, hope that is OK

#30 by M. F. Hasler at Mon Mar 18 18:28:05 EDT 2019

STATUS

editing

proposed

#29 by M. F. Hasler at Mon Mar 18 18:27:05 EDT 2019

PROG

(Python) def A248952(n): return min(A248939_row(n)); // M. F. Hasler, Mar 18 2019

#28 by M. F. Hasler at Mon Mar 18 18:20:10 EDT 2019

COMMENTS

Starting at n, a(n) is the minimum value reached according to the following rules. On the k-th step (k = smallest term 1, 2, 3, ...) move a distance of k in row n the direction of zero. If the number landed on has been landed on before, move a distance of triangle k away from zero instead. See A228474 and A248939;. - _David Nacin_, Mar 15 2019

a(A000217(n)) = 0; a(A014132(n)) < 0.

Starting at n, a(n) is the minimum point visited according to the following rules. On the k-th step (k = 1, 2, 3, ...) move a distance of k in the direction of zero. If the number landed on has been landed on before, move a distance of k away from zero instead. See A228474. - David Nacin, Mar 15 2019

It is currently unproved whether all orbits are finite, and therefore unclear whether all a(n) are well defined. In particular, the orbit of n = 11281 is of unknown length > 32*10^9 steps. - M. F. Hasler, Mar 18 2019

FORMULA

a(n) = smallest term in row n of triangle A248939;

a(A000217(n)) = 0; a(A014132(n)) < 0.

STATUS

proposed

editing

Discussion

Mon Mar 18

18:25

M. F. Hasler: I would tend to suggest to replace the quite lengthy (and anyway completely inefficient) Python code, duplicated in several sequences, by a simple (= #actual sequence):  a(n) = min( A248939_row(n)), where  A248939_row should return the orbit of n. (which is exactly what is stored in the array "spots" within the collection returned by the  trip() function.