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

1,1

Comments

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

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

Links

Table of n, a(n) for n=1..32.

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 *)

Crossrefs

Cf. A002110, A067024, A067027.

Sequence in context: A189080 A039113 A130399 * A348524 A096829 A265126

Adjacent sequences: A067023 A067024 A067025 * A067027 A067028 A067029

Keyword

nonn

Author

Labos Elemer, Dec 29 2001

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

Status

approved