A088764 a(n) = (A087680(n)-1)/2.

3, 4, 7, 13, 16, 28, 31, 37, 46, 52, 67, 76, 88, 97, 118, 133, 136, 181, 196, 202, 217, 226, 241, 247, 283, 286, 298, 301, 328, 343, 352, 361, 373, 382, 412, 457, 466, 493, 508, 517, 532, 556, 583, 598, 613, 616, 643, 646, 661, 688, 721, 727, 742, 763, 781, 787

Offset: 1

Author

Ray Chandler, Oct 26 2003

Keywords

• nonn

Links

• Vincenzo Librandi, Table of n, a(n) for n = 1..3575

Crossrefs

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

Programs

Magma

[(n-1)/2: n in [2..2000] |IsPrime(n+4) and IsPrime(n-4)]; // Vincenzo Librandi, May 19 2017

Mathematica

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