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

Author

Artur Jasinski, Apr 21 2008

Keywords

• nonn

Comments

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

Crossrefs

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

Programs

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 *)

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