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A089192 Numbers n such that 2n - 7 is a prime. 25


%S 5,6,7,9,10,12,13,15,18,19,22,24,25,27,30,33,34,37,39,40,43,45,48,52,

%T 54,55,57,58,60,67,69,72,73,78,79,82,85,87,90,93,94,99,100,102,103,

%U 109,115,117,118,120,123,124,129,132,135,138,139,142,144,145,150,157,159,160

%N Numbers n such that 2n - 7 is a prime.

%C Solutions of the equation (2*n-7)' = 1, where n' is the arithmetic derivative of n. - _Paolo P. Lava_, Nov 15 2012

%D M. Cerasoli, F. Eugeni and M. Protasi, Elementi di Matematica Discreta, Bologna 1988

%D Emanuele Munarini and Norma Zagaglia Salvi, Matematica Discreta, UTET, CittaStudiEdizioni, Milano 1997

%H Shawn A. Broyles, <a href="/A089192/b089192.txt">Table of n, a(n) for n = 1..1000</a>

%t lst={};Do[If[PrimeQ[2*n-7], (*Print[n];*)AppendTo[lst, n]], {n, 6!}];lst (* _Vladimir Joseph Stephan Orlovsky_, Aug 26 2008 *)

%t Select[Range[3,200],PrimeQ[2#-7]&] (* _Harvey P. Dale_, Aug 24 2014 *)

%o (PARI) is(n)=isprime(2*n - 7) \\ _Charles R Greathouse IV_, Apr 28 2015

%Y Numbers n such that 2n+k is prime: A005097 (k=1), A067076 (k=3), A089038 (k=5), A105760 (k=7), A155722 (k=9), A101448 (k=11), A153081 (k=13), A089559 (k=15), A173059 (k=17), A153143 (k=19).

%Y Numbers n such that 2n-k is prime: A006254 (k=1), A098090 (k=3), A089253 (k=5), this sequence (k=7), A097069 (k=9), A097338 (k=11), A097363 (k=13), A097480 (k=15), A098605 (k=17), A097932 (k=19).

%K easy,nonn

%O 1,1

%A _Giovanni Teofilatto_, Dec 08 2003

%E Corrected by _Ralf Stephan_, Mar 03 2004

%E Further correction from _Jeremy Gardiner_, Sep 11 2004

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Last modified September 20 10:49 EDT 2019. Contains 327229 sequences. (Running on oeis4.)