The On-Line Encyclopedia of Integer Sequences (OEIS)

Revision History for A319419 (Bold, blue-underlined text is an addition; faded, red-underlined text is a ~~deletion~~.)
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A319419

In binary expansion of n, delete one symbol from each run. Set a(n)=-1 if the result is the empty string.
(history; published version)

#22 by N. J. A. Sloane at Mon Feb 04 11:25:53 EST 2019

STATUS

editing

approved

#21 by N. J. A. Sloane at Mon Feb 04 11:25:51 EST 2019

LINKS

N. J. A. Sloane, Coordination Sequences, Planing Numbers, and Other Recent Sequences (II), Experimental Mathematics Seminar, Rutgers University, Jan 31 2019, <a href="https://vimeo.com/314786942">Part I</a>, <a href="https://vimeo.com/314790822">Part 2</a>, <a href="https://oeis.org/A320487/a320487.pdf">Slides.</a> (Mentions this sequence)

STATUS

approved

editing

#20 by N. J. A. Sloane at Mon Sep 24 02:04:12 EDT 2018

STATUS

proposed

approved

#19 by Chai Wah Wu at Mon Sep 24 00:07:59 EDT 2018

STATUS

editing

proposed

#18 by Chai Wah Wu at Mon Sep 24 00:07:55 EDT 2018

PROG

from re import split

STATUS

proposed

editing

#17 by Chai Wah Wu at Mon Sep 24 00:07:12 EDT 2018

STATUS

editing

proposed

#16 by Chai Wah Wu at Mon Sep 24 00:07:06 EDT 2018

PROG

return -1 if s == '' else int(s, 2) # Chai Wah Wu, Sep 24 2018

#15 by Chai Wah Wu at Mon Sep 24 00:06:47 EDT 2018

PROG

(Python)

def A319419(n):

s = ''.join(d[:-1] for d in split('(0+)|(1+)', bin(n)[2:]) if d not in {'', '0', '1', None})

return -1 if s == '' else int(s, 2) # Chai Wah Wu, Sep 24 2018

STATUS

approved

editing

#14 by N. J. A. Sloane at Sat Sep 22 00:02:44 EDT 2018

STATUS

editing

approved

#13 by N. J. A. Sloane at Sat Sep 22 00:02:42 EDT 2018

COMMENTS

A175046 expands the runs in a similar way, and a(A175046(n)) = A001477(n). - Andrew Weimholt, Sep 08 2018 (Comment copied from A318921.)

a(n) = -1 iff n in A000975.

CROSSREFS

Cf. A000975, A175046, A318921.

STATUS

approved

editing