A067026 (Prime(n)# - 4)/2 is prime, where x# is the primorial A034386(x).

3, 4, 5, 6, 7, 8, 9, 11, 13, 16, 20, 27, 39, 83, 103, 122, 129, 145, 279, 393, 608, 798, 929, 1164, 1266, 1491, 2043, 3276, 3426, 7119, 15711, 18424

Offset: 1

Author

Labos Elemer, Dec 29 2001

Keywords

• nonn

Comments

n such that A002110(n)/2 - 2 is prime.

a(33) > 25000. - Robert Price, Sep 29 2017

Crossrefs

Cf. A002110, A067024, A067027.

Programs

Mathematica

p = 1; Do[p = p*Prime[n]; If[PrimeQ[(p - 4)/2], Print[n]], {n, 1, 400} ]
Flatten[Position[Rest[FoldList[Times,1,Prime[Range[2100]]]],?(PrimeQ[(#-4)/2]&)]] (* _Harvey P. Dale, Nov 22 2014 *)

Extensions

More terms from Robert G. Wilson v, Dec 30 2001

a(21)-a(27) from Ray Chandler, Jun 16 2013

a(28)-a(32) from Robert Price, Sep 29 2017