The On-Line Encyclopedia of Integer Sequences (OEIS)

Revision History for A260855

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A260855

Base-5 representation of a(n) is the concatenation of the base-5 representations of 1, 2, ..., n, n-1, ..., 1.
(history; published version)

#13 by Joerg Arndt at Sat Jun 29 11:23:34 EDT 2019

STATUS

reviewed

approved

#12 by Michel Marcus at Sat Jun 29 11:22:48 EDT 2019

STATUS

proposed

reviewed

#11 by Jon E. Schoenfield at Sat Jun 29 11:05:28 EDT 2019

STATUS

editing

proposed

#10 by Jon E. Schoenfield at Sat Jun 29 11:05:26 EDT 2019

NAME

Numbers whose baseBase-5 representation of a(n) is the concatenation of the base-5 representation representations of 1, 2, ..., n, n-1, ..., 1.

STATUS

proposed

editing

#9 by Jon E. Schoenfield at Sat Jun 29 10:49:40 EDT 2019

STATUS

editing

proposed

#8 by Jon E. Schoenfield at Sat Jun 29 10:49:37 EDT 2019

NAME

Base Numbers whose base-5 representation is the concatenation of the base -5 representation of 1, 2, ..., n, n-1, ..., 1.

COMMENTS

Base -5 variant of A173426 (base 10) and A173427 (base 2). See A260853 - A260866 for variants in other bases b = 3, ..., 16.

EXAMPLE

a(2) = 36 = (5+1)^2 = 5^2 + 2*5 + 1 = 121[_4] is the concatenation of (1, 2, 1).

a(5) = 3034961 = 1234104321[_5] is the concatenation of (1, 2, 3, 4, 10, 4, 3, 2, 1), where the middle "10" is the base -5 representation of 5.

STATUS

approved

editing

#7 by R. J. Mathar at Mon Sep 10 15:04:32 EDT 2018

STATUS

editing

approved

#6 by R. J. Mathar at Mon Sep 10 15:04:28 EDT 2018

LINKS

D. Broadhurst, <a href="https://listserv.nodak.edu/cgi-bin/wa.exe?A2=ind1508&L=NMBRTHRY&F=&S=&P=521af419558.150">Primes from concatenation: results and heuristics</a>, NmbrThry List, August 1, 2015

STATUS

approved

editing

#5 by M. F. Hasler at Thu Aug 06 19:11:19 EDT 2015

STATUS

editing

approved

#4 by M. F. Hasler at Sun Aug 02 17:05:32 EDT 2015

COMMENTS

Base 5 variant of A173426 (base 10) and A173427 (base 2). See A260853 - A260866 for variants in other bases b = 3, ..., 16.

The base 5 is not listed in A260343, because a(5) = A260851(5) = 3034961 is not prime and therefore not in A260852. See these sequences for more information.

LINKS

D. Broadhurst, <a href="https://listserv.nodak.edu/cgi-bin/wa.exe?A2=ind1508&L=NMBRTHRY&F=&S=&P=9999521">Primes from concatenation: results and heuristics</a>, NmbrThry List, August 1, 2015