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%I #11 Sep 29 2012 18:18:22
%S 17,37,41,53,67,71,79,89,97,113,131,157,163,211,223,239,251,269,293,
%T 307,311,331,337,367,373,379,397,409,419,439,449,487,491,499,521,547,
%U 593,599,613,631,673,683,691,701,709,733,739,751,757,769,773,787,809
%N Primes p such that p-2 is the greatest semiprime less than p.
%C This is a subsequence of A063638.
%H T. D. Noe, <a href="/A217195/b217195.txt">Table of n, a(n) for n = 1..1000</a>
%e 487 is prime, 486 = 2*3^5 is not semiprime and 485 = 5*97 is semiprime.
%t SemiPrimeQ[n_Integer] := If[Abs[n] < 2, False, (2 == Plus @@ Transpose[FactorInteger[Abs[n]]][[2]])]; Select[Prime[Range[200]], ! SemiPrimeQ[# - 1] && SemiPrimeQ[# - 2] &] (* _T. D. Noe_, Sep 27 2012 *)
%o (PARI) forprime(p=3, 9999, bigomega(p-2)==2 && bigomega(p-1)!=2 & print1(p", "))
%K nonn
%O 1,1
%A _Antonio Roldán_, Sep 27 2012
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