The On-Line Encyclopedia of Integer Sequences (OEIS)

Revision History for A191647 (Bold, blue-underlined text is an addition; faded, red-underlined text is a ~~deletion~~.)
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A191647

Numbers n with property that the concatenation of their anti-divisors is a prime.
(history; published version)

#32 by N. J. A. Sloane at Sat Dec 07 12:18:26 EST 2019

PROG

[n for n in xrangerange(3, 10**4) if isprime(int(''.join([str(d) for d in xrangerange(2, n) if n%d and 2*n%d in [d-1, 0, 1]])))] # Chai Wah Wu, Aug 08 2014

Discussion

Sat Dec 07

12:18

OEIS Server: https://oeis.org/edit/global/2837

#31 by OEIS Server at Wed Feb 28 12:03:25 EST 2018

LINKS

Klaus Brockhaus <a href="/A191647/b191647_2.txt">Table of n, a(n) for n = 1..1000</a> (first 250 terms from Paolo P. Lava)

#30 by Bruno Berselli at Wed Feb 28 12:03:25 EST 2018

STATUS

editing

approved

Discussion

Wed Feb 28

12:03

OEIS Server: Installed new b-file as b191647.txt.  Old b-file is now b191647_2.txt.

#29 by Bruno Berselli at Wed Feb 28 12:02:33 EST 2018

EXTENSIONS

Corrected a(618) corrected in b-file by Paolo P. Lava, Feb 28 2018

#28 by Bruno Berselli at Wed Feb 28 12:00:01 EST 2018

LINKS

Paolo P. Lava and Klaus Brockhaus <a href="/A191647/b191647_2.txt">Table of n, a(n) for n = 1..1000</a> (first 250 terms from Paolo P. Lava)

#27 by Bruno Berselli at Wed Feb 28 10:41:01 EST 2018

STATUS

proposed

editing

#26 by Paolo P. Lava at Wed Feb 28 02:12:27 EST 2018

STATUS

editing

proposed

#25 by Paolo P. Lava at Wed Feb 28 02:04:52 EST 2018

MAPLE

with(numtheory):

P:=proc(i) local a, b, c, d, k, n, s, v; v:=array(1..200000);

local a, b, c, d, k, n, s, v;

v:=array(1..200000);

for n from 3 by 1 to i do k:=2; b:=0;

while k<n do if (k:= mod 2; b:)=0; then

while k<n do

if (k mod 2)=0 then

if (n mod k)>0 and (((2*n-1) mod k)=0 or ((2*n+1) mod k)=0) then b:=b+1; v[b]:=k; fi;

fi;

b:=b+1; v[b]:=k; fi; fi; k:=k+1; od; a:=v[1];

od;

a:=v[1];

od; end: P(10^6);

end:

P(2000);

EXTENSIONS

Corrected b-file by Paolo P. Lava, Feb 28 2018

#24 by Paolo P. Lava at Wed Feb 28 02:01:46 EST 2018

LINKS

Paolo P. Lava, and Klaus Brockhaus <a href="/A191647/b191647_2.txt">Table of n, a(n) for n = 1..1000</a>

#23 by Paolo P. Lava at Wed Feb 28 02:00:25 EST 2018

LINKS

Paolo P. Lava and Klaus Brockhaus, , <a href="/A191647/b191647_2.txt">Table of n, a(n) for n = 1..1000</a>

STATUS

approved

editing