The On-Line Encyclopedia of Integer Sequences (OEIS)

Revision History for A061873 (Bold, blue-underlined text is an addition; faded, red-underlined text is a ~~deletion~~.)
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A061873

Numbers n such that |first digit - second digit + third digit - fourth digit ...| = 4.
(history; published version)

#10 by Michel Marcus at Fri Apr 16 02:11:27 EDT 2021

STATUS

reviewed

approved

#9 by Joerg Arndt at Fri Apr 16 01:36:51 EDT 2021

STATUS

proposed

reviewed

#8 by Michael S. Branicky at Thu Apr 15 13:31:12 EDT 2021

STATUS

editing

proposed

#7 by Michael S. Branicky at Thu Apr 15 13:23:50 EDT 2021

PROG

(Python)

def ok(n): return abs(sum((-1)**i*int(d) for i, d in enumerate(str(n))))==4

print(list(filter(ok, range(456)))) # Michael S. Branicky, Apr 15 2021

STATUS

approved

editing

#6 by Joerg Arndt at Sat Jun 04 01:49:32 EDT 2016

STATUS

proposed

approved

#5 by Robert Israel at Fri Jun 03 17:00:31 EDT 2016

STATUS

editing

proposed

#4 by Robert Israel at Fri Jun 03 16:59:09 EDT 2016

COMMENTS

All terms == 4 or 7 (mod 11). - Robert Israel, Jun 03 2016

LINKS

Robert Israel, <a href="/A061873/b061873.txt">Table of n, a(n) for n = 1..10000</a>

MAPLE

F:= proc(n) option remember;

-procname(floor(n/10)) + (n mod 10)

end proc:

for j from 0 to 9 do F(j):= j od:

select(abs @ F = 4, [$1..1000]); # Robert Israel, Jun 03 2016

STATUS

approved

editing

#3 by Russ Cox at Fri Mar 30 17:30:32 EDT 2012

AUTHOR

_Robert G. Wilson v (rgwv(AT)rgwv.com), _, May 10 2001

Discussion

Fri Mar 30

17:30

OEIS Server: https://oeis.org/edit/global/156

#2 by N. J. A. Sloane at Fri Sep 29 03:00:00 EDT 2006

NAME

Numbers n such that |First first digit - second digit + third digit - fourth digit ...| = 4.

KEYWORD

nonn,base,easy,new

#1 by N. J. A. Sloane at Fri May 16 03:00:00 EDT 2003

NAME

|First digit - second digit + third digit - fourth digit ...| = 4.

DATA

4, 15, 26, 37, 40, 48, 51, 59, 62, 73, 84, 95, 103, 114, 125, 136, 147, 150, 158, 161, 169, 172, 183, 194, 202, 213, 224, 235, 246, 257, 260, 268, 271, 279, 282, 293, 301, 312, 323, 334, 345, 356, 367, 370, 378, 381, 389, 392, 400, 411, 422, 433, 444, 455

OFFSET

1,1

MATHEMATICA

Do[ a = IntegerDigits[ n ]; l = Length[ a ]; e = o = {}; Do[ o = Append[ o, a[ [ 2k - 1 ] ] ], {k, 1, l/2 + .5} ]; Do[ e = Append[ e, a[ [ 2k ] ] ], {k, 1, l/2} ]; If[ Abs[ Apply[ Plus, o ] - Apply[ Plus, e ] ] == 4, Print[ n ] ], {n, 1, 1000} ]

CROSSREFS

Cf. A008593, A060978-A060980, A060982, A061470-A061479, A061870-A061882.

KEYWORD

nonn,base,easy

AUTHOR

Robert G. Wilson v (rgwv(AT)rgwv.com), May 10 2001

STATUS

approved