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A168063 Numbers n such that exactly two of {n-2, n-1, n+1, n+2} are primes. 2


%S 1,3,5,6,9,12,15,18,21,30,39,42,45,60,69,72,81,99,102,105,108,111,129,

%T 138,150,165,180,192,195,198,225,228,231,240,270,279,282,309,312,315,

%U 348,351,381,399,420,432,441,459,462,465,489,501,522,570,600,615,618

%N Numbers n such that exactly two of {n-2, n-1, n+1, n+2} are primes.

%C Essentially the same as A014574 U A087679. - _Charles R Greathouse IV_, May 25, 2011

%H G. C. Greubel, <a href="/A168063/b168063.txt">Table of n, a(n) for n = 1..1000</a>

%t Select[Range[700],Count[#+{-2,-1,1,2},_?PrimeQ]==2&] (* _Harvey P. Dale_, Jan 24 2014 *)

%K nonn,easy

%O 1,2

%A _Juri-Stepan Gerasimov_, Nov 18 2009

%E Corrected (105 inserted, 609 removed) by _R. J. Mathar_, Jun 04 2010

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Last modified December 4 21:30 EST 2020. Contains 338939 sequences. (Running on oeis4.)