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A098571
a(n) is the least k such that Mersenne-prime(n)*prime(k)# + 1 is prime, where prime(k)# is the k-th primorial.
1
1, 2, 6, 6, 16, 5, 3, 4, 5, 33, 29, 24, 31, 124, 290, 103, 370, 186, 4654, 133, 221, 244, 206, 726, 601, 18
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