A139456 Numbers n such that primorial(n)/2 - 1024 is prime.

5, 9, 10, 11, 16, 17, 20, 59, 96, 98, 318, 387, 938, 978, 1764, 8298, 10632, 11796, 19982

Offset

1,1

Comments

a(20) > 25000. - Robert Price, Sep 28 2017

Links

Table of n, a(n) for n=1..19.

Mathematica

k = 1; a = {}; Do[k = k*Prime[n]; If[PrimeQ[k - 1024]&&k>1024, Print[n]; AppendTo[a, n]], {n, 2, 325}]; a
Drop[Flatten[Position[FoldList[Times, Prime[Range[400]]], _?(PrimeQ[#/2-1024]&)]], 3] (* The program generates the first 12 terms of the sequence. To generate more, increase the Range constant but the program may take a long time to run. *) (* Harvey P. Dale, Sep 15 2023 *)

Crossrefs

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

Sequence in context: A043682 A335882 A111102 * A195684 A135980 A314579

Adjacent sequences: A139453 A139454 A139455 * A139457 A139458 A139459

Keyword

nonn

Author

Artur Jasinski, Apr 21 2008

Extensions

Drop 2,3,4 and correct program, a(12)-a(15) from Ray Chandler, Jun 16 2013

a(16)-a(19) from Robert Price, Sep 28 2017

Status

approved