A087680 - OEIS

%I #28 May 21 2023 19:12:20

%S 7,9,15,27,33,57,63,75,93,105,135,153,177,195,237,267,273,363,393,405,

%T 435,453,483,495,567,573,597,603,657,687,705,723,747,765,825,915,933,

%U 987,1017,1035,1065,1113,1167,1197,1227,1233,1287,1293,1323,1377,1443

%N Numbers n such that n + 4 and n - 4 are both prime.

%C All terms > 7 (prime) are divisible by 3. Also note that n-4 and n+4 are not necessarily consecutive primes. First case when n-4 and n+4 are consecutive primes is for n=93 with n-4=89 and n+4=97. - _Zak Seidov_, Apr 22 2015

%H Daniel Starodubtsev, <a href="/A087680/b087680.txt">Table of n, a(n) for n = 1..10000</a>

%F a(n) = A023202(n) + 4. - _Michel Marcus_, Apr 22 2015

%p ZL:=[]:for p from 1 to 1444 do if (isprime(p) and isprime(p+8) ) then ZL:=[op(ZL),(p+(p+8))/2]; fi; od; print(ZL); # _Zerinvary Lajos_, Mar 07 2007

%t f[n_]:=PrimeQ[n-4]&&PrimeQ[n+4]; lst={};Do[If[f[n],AppendTo[lst,n]],{n,3,8!,2}];lst (* _Vladimir Joseph Stephan Orlovsky_, Oct 09 2009 *)

%t Select[Prime[Range[250]],PrimeQ[#+8]&]+4 (* _Harvey P. Dale_, May 21 2023 *)

%Y Cf. A023202, A014574, A087678-A087683, A087695-A087697, A088764.

%K easy,nonn

%O 1,1

%A _Zak Seidov_, Sep 27 2003

%E More terms from _Ray Chandler_, Oct 26 2003