OFFSET
1,2
MATHEMATICA
f[p_] := Module[{k = 1, q = r = 2}, While[! PrimeQ[r*p + 1], q = NextPrime[q]; r *= q; k++]; k]; f /@ (2^MersennePrimeExponent[Range[15]] - 1) (* Amiram Eldar, Aug 28 2021 *)
CROSSREFS
KEYWORD
nonn,more
AUTHOR
Pierre CAMI, Sep 16 2004
EXTENSIONS
a(19)-a(26) from Amiram Eldar, Aug 28 2021
STATUS
approved