A139449 Numbers n such that primorial(n)/2 + 128 is prime.

2, 4, 5, 7, 8, 10, 11, 23, 25, 67, 87, 125, 141, 242, 255, 258, 279, 316, 449, 578, 871, 1072, 1886, 2071, 3315, 18225

Offset: 1

Author

Artur Jasinski, Apr 21 2008

Keywords

• nonn

Comments

a(27) > 25000. - Robert Price, Apr 10 2017

Crossrefs

Cf. A067026, A067027, A139439-A139457, A103514.

Programs

Mathematica

k = 1/2; a = {}; Do[k = k*Prime[n]; If[PrimeQ[k + 128], Print[n]; AppendTo[a, n]], {n, 325}]; a
Select[Range[0, 25000], PrimeQ[Product[Prime[k], {k, 1, #}]/2 + 128] &] (* Robert Price, Apr 10 2017 *)

Extensions

a(18)-a(24) from Ray Chandler, Jun 16 2013

a(25)-a(26) from Robert Price, Apr 10 2017