The On-Line Encyclopedia of Integer Sequences (OEIS)

Revision History for A172258 (Bold, blue-underlined text is an addition; faded, red-underlined text is a ~~deletion~~.)
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A172258

Primes p such that exactly one of the numbers 2p-3 and 2p+3 is prime.
(history; published version)

#12 by Harvey P. Dale at Sat Mar 27 14:57:44 EDT 2021

STATUS

editing

approved

#11 by Harvey P. Dale at Sat Mar 27 14:57:42 EDT 2021

LINKS

Harvey P. Dale, <a href="/A172258/b172258.txt">Table of n, a(n) for n = 1..1000</a>

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approved

editing

#10 by Harvey P. Dale at Sat Mar 27 14:56:34 EDT 2021

STATUS

editing

approved

#9 by Harvey P. Dale at Sat Mar 27 14:56:31 EDT 2021

MATHEMATICA

Select[Prime[Range[100]], Total[Boole[PrimeQ[2#+{3, -3}]]]==1&] (* Harvey P. Dale, Mar 27 2021 *)

STATUS

approved

editing

#8 by Joerg Arndt at Tue Jan 22 02:50:23 EST 2019

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proposed

approved

#7 by Michel Marcus at Tue Jan 22 00:11:14 EST 2019

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editing

proposed

#6 by Michel Marcus at Tue Jan 22 00:11:09 EST 2019

EXAMPLE

a(1)=2 because 2*2-3=1 (nonprime) and 2*2+3=7 (prime); a(2)=29 because 2*29-3=55(nonprime) and 2*29+3=61(prime).

a(2)=29 because 2*29-3=55 (nonprime) and 2*29+3=61 (prime).

CROSSREFS

Cf. A000040, A092110, A131426.

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proposed

editing

#5 by Jon E. Schoenfield at Mon Jan 21 23:16:21 EST 2019

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editing

proposed

#4 by Jon E. Schoenfield at Mon Jan 21 23:16:16 EST 2019

MAPLE

a := proc (n): if isprime(n) = true and isprime(2*n-3) = true and isprime(2*n+3) = false then n elif isprime(n) = true and isprime(2*n-3) = false and isprime(2*n+3) = true then n else end if end proc: seq(a(n), n = 1 .. 700); [From _# _Emeric Deutsch_, Feb 15 2010]

STATUS

approved

editing

#3 by Russ Cox at Fri Mar 30 18:52:39 EDT 2012

AUTHOR

_Juri-Stepan Gerasimov (2stepan(AT)rambler.ru), _, Jan 30 2010

Discussion

Fri Mar 30

18:52

OEIS Server: https://oeis.org/edit/global/257