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%I #27 Feb 04 2024 01:17:09
%S 6,7,8,10,11,13,14,16,19,20,23,25,26,28,31,34,35,38,40,41,44,46,49,53,
%T 55,56,58,59,61,68,70,73,74,79,80,83,86,88,91,94,95,100,101,103,104,
%U 110,116,118,119,121,124,125,130,133,136,139,140,143,145,146,151,158,160
%N Positive integers n such that 2n - 9 is prime.
%H Vincenzo Librandi, <a href="/A097069/b097069.txt">Table of n, a(n) for n = 1..1000</a>
%F Half of p+9 where p is a prime greater than 2.
%t (Prime[Range[2,100]]+9)/2 (* _Vladimir Joseph Stephan Orlovsky_, Feb 08 2010 *)
%t Select[Range[4, 200], PrimeQ[2 # - 9] &] (* _Vincenzo Librandi_, Oct 16 2012 *)
%o (Magma) [n: n in [6..160] | IsPrime(2*n-9)]; // _Bruno Berselli_, Mar 05 2011
%o (PARI) is(n)=isprime(2*n-9) \\ _Charles R Greathouse IV_, Apr 28 2015
%Y Cf. A000040, A086801.
%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), A089192 (k=7), this seq(k=9), A097338 (k=11), A097363 (k=13), A097480 (k=15), A098605 (k=17), A097932 (k=19).
%K easy,nonn
%O 1,1
%A Douglas Winston (douglas.winston(AT)srupc.com), Sep 15 2004
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