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a(n) = (A087680(n)-1)/2.
6

%I #16 May 21 2023 19:14:04

%S 3,4,7,13,16,28,31,37,46,52,67,76,88,97,118,133,136,181,196,202,217,

%T 226,241,247,283,286,298,301,328,343,352,361,373,382,412,457,466,493,

%U 508,517,532,556,583,598,613,616,643,646,661,688,721,727,742,763,781,787

%N a(n) = (A087680(n)-1)/2.

%H Vincenzo Librandi, <a href="/A088764/b088764.txt">Table of n, a(n) for n = 1..3575</a>

%t f[n_]:=PrimeQ[n - 4] && PrimeQ[n + 4]; lst={}; Do[If[f[n], AppendTo[lst, (n - 1) / 2]], {n, 3, 7!, 2}]; lst (* _Vincenzo Librandi_, May 19 2017 *)

%t (#-1)/2&/@(Select[Prime[Range[250]],PrimeQ[#+8]&]+4) (* _Harvey P. Dale_, May 21 2023 *)

%o (Magma) [(n-1)/2: n in [2..2000] |IsPrime(n+4) and IsPrime(n-4)]; // _Vincenzo Librandi_, May 19 2017

%Y Cf. A087680, A088762, A088766, A088768, A088770.

%K nonn

%O 1,1

%A _Ray Chandler_, Oct 26 2003