A118068 Numbers k such that A103557(k)*((prime(k)#)^2) - 1 is a Sophie Germain prime, where prime(k)# is the k-th primorial.

1, 7, 8, 13, 26, 58

Offset

1,2

Comments

a(7) > 200. - Amiram Eldar, Sep 11 2021

Links

Table of n, a(n) for n=1..6.

Mathematica

q[n_] := Module[{p2 = Product[Prime[i], {i, 1, n}]^2, k=1}, While[!PrimeQ[k*p2-1] || !PrimeQ[k*p2+1], k++]; PrimeQ[2*k*p2 - 1]]; Select[Range[100], q] (* Amiram Eldar, Sep 11 2021 *)

Crossrefs

Cf. A002110, A005384, A103557.

Sequence in context: A025156 A228210 A045765 * A060754 A196129 A286261

Adjacent sequences: A118065 A118066 A118067 * A118069 A118070 A118071

Keyword

nonn,hard,more

Author

Pierre CAMI, May 11 2006

Extensions

Data corrected by Amiram Eldar, Sep 11 2021

Status

approved