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A118068
Numbers k such that A103557(k)*((prime(k)#)^2) - 1 is a Sophie Germain prime, where prime(k)# is the k-th primorial.
0
1, 7, 8, 13, 26, 58
OFFSET
1,2
COMMENTS
a(7) > 200. - Amiram Eldar, Sep 11 2021
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
KEYWORD
nonn,hard,more
AUTHOR
Pierre CAMI, May 11 2006
EXTENSIONS
Data corrected by Amiram Eldar, Sep 11 2021
STATUS
approved