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A140546 Primes p such that neither p - 6 nor p + 6 is prime.

%I A140546 #12 Jul 12 2025 12:33:13
%S A140546 2,3,71,127,139,149,181,211,241,281,293,349,397,401,409,419,421,431,
%T A140546 479,487,491,499,521,523,617,631,643,661,673,691,701,709,719,743,761,
%U A140546 769,773,787,797,809,811,839,907,911,919,929,937,967,1009,1021,1031,1049
%N A140546 Primes p such that neither p - 6 nor p + 6 is prime.
%H A140546 N. J. A. Sloane, <a href="/A140546/b140546.txt">Table of n, a(n) for n = 1..10000</a>
%p A140546 isA140546 := proc(n)
%p A140546     if isprime(n) then
%p A140546         if isprime(n+6) or isprime(n-6) then
%p A140546             false;
%p A140546         else
%p A140546             true;
%p A140546         end if;
%p A140546     else
%p A140546         false ;
%p A140546     end if;
%p A140546 end proc:
%p A140546 A140546 := proc(n)
%p A140546     option remember;
%p A140546     local a;
%p A140546     if n = 1 then
%p A140546         2 ;
%p A140546     else
%p A140546         a := nextprime(procname(n-1)) ;
%p A140546         while true do
%p A140546             if isA140546(a) then
%p A140546                 return a;
%p A140546             else
%p A140546                 a := nextprime(a) ;
%p A140546             end if;
%p A140546         end do:
%p A140546     end if;
%p A140546 end proc:
%p A140546 seq(A140546(n),n=1..80) ; # _R. J. Mathar_, Jun 10 2024
%t A140546 Select[Prime[Range[176]],!PrimeQ[#+6]&&(!PrimeQ[#-6]||#<5)&] (* _James C. McMahon_, Jul 12 2025 *)
%Y A140546 Cf. A136207 (complement)
%K A140546 nonn,easy
%O A140546 1,1
%A A140546 _Juri-Stepan Gerasimov_, Jun 30 2008
%E A140546 Corrected and extended by _Charles R Greathouse IV_, Mar 25 2010