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

1,1

Comments

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

Links

Table of n, a(n) for n=1..26.

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 *)

Crossrefs

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

Sequence in context: A370277 A102338 A285401 * A204399 A020914 A195176

Adjacent sequences: A139446 A139447 A139448 * A139450 A139451 A139452

Keyword

nonn

Author

Artur Jasinski, Apr 21 2008

Extensions

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

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

Status

approved