OFFSET
1,4
MATHEMATICA
f[p_] := Module[{m = 1, k = 2, q = 2}, While[!PrimeQ[k*p - 1], q = NextPrime[q]; k *= q; m++]; m]; f /@ (2^MersennePrimeExponent[Range[15]] - 1) (* Amiram Eldar, Jul 25 2021 *)
CROSSREFS
KEYWORD
nonn,more
AUTHOR
Pierre CAMI, Sep 16 2004
EXTENSIONS
a(21)-a(23) from Amiram Eldar, Jul 25 2021
STATUS
approved